ISPATHSEP and ISTILDE macros; Windows portability

Windows treats '\\' and '/' equivalently but we cannot control
the form that will be used by end users.  Introduce ISPATHSEP()
macro which tests only for '/' on UNIX and both on Windows.
Introduce ISTILDE() macro to test for '~'.   When testing for
'/' with strchr() or strrchr() add conditional checks for '\\' on
Windows.

Change-Id: Ia85e698fc88f15a6a71db649db5417f02ef7e5fe

lib/krb5/krb5_locl.h

@@ -375,4 +375,11 @@ enum krb5_pk_type {
 
 #endif /* PKINIT */
 
+#define ISTILDE(x) (x == '~')
+#ifdef _WIN32
+# define ISPATHSEP(x) (x == '/' || x =='\\')
+#else
+# define ISPATHSEP(x) (x == '/')
+#endif
+
 #endif /* __KRB5_LOCL_H__ */