Move some infra bits of lib/krb5/ to lib/base/ (2)

This is the second of two commits in a series that must be picked together.

This series of two commits moves parts of lib/krb5/ infrastructure
functionality to lib/base/, leaving behind wrappers.

Some parts of libkrb5 are entirely generic or easily made so, and could
be useful in various parts of Heimdal that are not specific to the krb5
API, such as:

 - lib/gssapi/  (especially since the integration of NegoEx)
 - lib/hx509/
 - bx509d       (which should really move out of kdc/)

For the above we need to move these bits of lib/krb5/:

 - lib/krb5/config_file.c   (all of it, leaving forwardings behind)
 - lib/krb5/config_reg.c    (all of it)
 - lib/krb5/plugin.c        (all of it, leaving forwardings behind)
 - lib/krb5/log.c           (all of it, ditto)
 - lib/krb5/heim_err.et     (all of it)

And because of those two, these too must also move:

 - lib/krb5/expand_path.c   (all of it, leaving forwardings behind)
 - lib/krb5/warn.c          (just the warning functions, ditto)

The changes to the moved files are mostly quite straightforward and are
best reviewed with --word-diff=color.

We're also creating a heim_context and a heim API to go with it.  But
it's as thin as possible, with as little state as necessary to enable
this move.  Functions for dealing with error messages use callbacks.

Moving plugin.c does have one knock-on effect on all users of the old
krb5 plugin API (which remains), which is that a global search and
replace of struct krb5_plugin_data to struct heim_plugin_data was
needed, though the layout and size of that structure doesn't change, so
the ABI doesn't either.

As well, we now build lib/vers/ and lib/com_err/ before lib/base/ so as
to be able to move lib/krb5/heim_err.et to lib/base/ so that we can make
use of HEIM_ERR_* in lib/base/, specifically in the files that moved.

Once this is all done we'll be able to use config files and plugins in
lib/hx509/, we'll be able to move bx509d out of kdc/, and so on.

Most if not all of the new functions in lib/base/ are Heimdal-private,
thus calling conventions for them are not declared.

Status:

 - builds and passes CIs (Travis, Appveyor)
 - ran make check-valgrind and no new leaks or other memory errors
 - ready for review

HOW TO REVIEW:

     $ # Review file moves:
     $ git log --stat -n1 HEAD^
     $
     $ # Review changes to moved files using --word-diff=color
     $ git log -p -b -w --word-diff=color HEAD^..HEAD   \
               lib/base/config_file.c                   \
               lib/base/config_reg.c                    \
               lib/base/expand_path.c                   \
               lib/base/warn.c                          \
               lib/krb5/config_file.c                   \
               lib/krb5/config_reg.c                    \
               lib/krb5/expand_path.c                   \
               lib/krb5/warn.c
     $
     $ # Review the whole thing, possibly adding -b and/or -w, and
     $ # maybe --word-diff=color:
     $ git log -p origin/master..HEAD
     $ git log -p -b -w origin/master..HEAD
     $ git log -p -b -w --word-diff=color origin/master..HEAD

TBD (future commits):

 - make lib/gssapi use the new heimbase functions
 - move kx509/bx509d common code to lib/hx509/ or other approp. location
 - move bx509d out of kdc/

lib/base/heimbase.h

@@ -55,8 +55,89 @@
 #endif
 #endif
 
+#include <stdint.h>
+
+#include <heim_err.h>
+
+#ifdef _WIN32
+#define HEIM_CALLCONV __stdcall
+#define HEIM_LIB_CALL __stdcall
+#else
+#define HEIM_CALLCONV
+#define HEIM_LIB_CALL
+#endif
+
+#if !defined(__GNUC__) && !defined(__attribute__)
+#define __attribute__(x)
+#endif
+
 #define HEIM_BASE_API_VERSION 20130210
 
+typedef int32_t heim_error_code;
+typedef struct heim_context_s *heim_context;
+typedef struct heim_pcontext_s *heim_pcontext;
+
+typedef void (HEIM_CALLCONV *heim_log_log_func_t)(heim_context,
+                                                  const char *,
+                                                  const char *,
+                                                  void *);
+typedef void (HEIM_CALLCONV *heim_log_close_func_t)(void *);
+
+struct heim_log_facility_internal {
+    int min;
+    int max;
+    heim_log_log_func_t log_func;
+    heim_log_close_func_t close_func;
+    void *data;
+};
+
+
+typedef struct heim_log_facility_s {
+    char *program;
+    int len;
+    struct heim_log_facility_internal *val;
+} heim_log_facility;
+
+typedef uintptr_t
+(HEIM_LIB_CALL *heim_get_instance_func_t)(const char *);
+
+#define HEIM_PLUGIN_INVOKE_ALL 1
+
+struct heim_plugin_data {
+    const char *module;
+    const char *name;
+    int min_version;
+    const char **deps;
+    heim_get_instance_func_t get_instance;
+};
+
+typedef struct heim_err_cb_context_s *heim_err_cb_context;
+typedef void (*heim_err_cb_clear_msg)(heim_err_cb_context);
+typedef void (*heim_err_cb_free_msg)(heim_err_cb_context, const char *);
+typedef const char * (*heim_err_cb_get_msg)(heim_err_cb_context, int32_t);
+typedef void (*heim_err_cb_set_msg)(heim_err_cb_context, int32_t,
+                                    const char *, va_list)
+    __attribute__ ((__format__ (__printf__, 3, 0)));
+
+typedef struct heim_config_binding heim_config_binding;
+struct heim_config_binding {
+    enum {
+        heim_config_string,
+        heim_config_list,
+        /* For compatibility in krb5 code */
+        krb5_config_string = heim_config_string,
+        krb5_config_list = heim_config_list,
+    } type;
+    char *name;
+    struct heim_config_binding *next;
+    union {
+        char *string;
+        struct heim_config_binding *list;
+        void *generic;
+    } u;
+};
+typedef struct heim_config_binding heim_config_section;
+
 typedef void * heim_object_t;
 typedef unsigned int heim_tid_t;
 typedef heim_object_t heim_bool_t;
@@ -572,4 +653,7 @@ heim_base_exchange_pointer(void *target, void *value)
 #error set SIZEOF_TIME_T for your platform
 #endif
 
+#include <heim_threads.h>
+#include <heimbase-protos.h>
+
 #endif /* HEIM_BASE_H */