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, 5 insertions, 2 deletions

diff --git a/mjit.h b/mjit.h
index 256bf65a29..44cb6571b7 100644
--- a/mjit.h
+++ b/mjit.h
@@ -9,11 +9,14 @@
 #ifndef RUBY_MJIT_H
 #define RUBY_MJIT_H 1
 
-#include "ruby.h"
-#include "debug_counter.h"
+#include "ruby/config.h"
 
 #if USE_MJIT
 
+#include "debug_counter.h"
+#include "ruby.h"
+#include "vm_core.h"
+
 // Special address values of a function generated from the
 // corresponding iseq by MJIT:
 enum rb_mjit_iseq_func {