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, 1 insertions, 1 deletions

diff --git a/gc.h b/gc.h
index cf794fa514..750d87819b 100644
--- a/gc.h
+++ b/gc.h
@@ -1,6 +1,6 @@
-
 #ifndef RUBY_GC_H
 #define RUBY_GC_H 1
+#include "ruby/ruby.h"
 
 #if defined(__x86_64__) && !defined(_ILP32) && defined(__GNUC__)
 #define SET_MACHINE_STACK_END(p) __asm__ __volatile__ ("movq\t%%rsp, %0" : "=r" (*(p)))