Make concurrent builds work.

To stop the errors when building concurrently, we make a number of
changes:

        1.  stop including generated files in *_SOURCES,

        2.  make *-protos.h and *-private.h depend on the *_SOURCES,

        3.  make all objects depend on *-{protos,private}.h,

        4.  in a few places change dir/header.h to $(srcdir)/dir/header.h,

This appears to work for me with make -j16 on a 4-way box.

appl/login/Makefile.am

@@ -12,7 +12,6 @@ login_SOURCES =					\
 		login.c				\
 		login_access.c			\
 		login_locl.h			\
-		login-protos.h			\
 		loginpaths.h			\
 		limits_conf.c			\
 		osfc2.c				\
@@ -32,7 +31,7 @@ LDADD = $(LIB_otp) \
 	$(LIB_security) \
 	$(DBLIB)
 
-$(srcdir)/login-protos.h:
+$(srcdir)/login-protos.h: $(login_SOURCES)
 	cd $(srcdir); perl ../../cf/make-proto.pl -o login-protos.h -q -P comment $(login_SOURCES) || rm -f login-protos.h
 
 $(login_OBJECTS): $(srcdir)/login-protos.h