decouple internal.h headers

Saves comitters' daily life by avoid #include-ing everything from
internal.h to make each file do so instead.  This would significantly
speed up incremental builds.

We take the following inclusion order in this changeset:

1.  "ruby/config.h", where _GNU_SOURCE is defined (must be the very
    first thing among everything).
2.  RUBY_EXTCONF_H if any.
3.  Standard C headers, sorted alphabetically.
4.  Other system headers, maybe guarded by #ifdef
5.  Everything else, sorted alphabetically.

Exceptions are those win32-related headers, which tend not be self-
containing (headers have inclusion order dependencies).

1 files changed, 4 insertions, 0 deletions

diff --git a/internal/string.h b/internal/string.h
index dae4f1bdc0..f585163594 100644
--- a/internal/string.h
+++ b/internal/string.h
@@ -19,6 +19,10 @@
 #define STR_NOEMBED      FL_USER1
 #define STR_SHARED       FL_USER2 /* = ELTS_SHARED */
 
+#ifdef rb_fstring_cstr
+# undef rb_fstring_cstr
+#endif
+
 /* string.c */
 VALUE rb_fstring(VALUE);
 VALUE rb_fstring_cstr(const char *str);