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, 3 insertions, 0 deletions

diff --git a/method.h b/method.h
index b26caaa92d..519cc9bfc1 100644
--- a/method.h
+++ b/method.h
@@ -12,6 +12,9 @@
 #define RUBY_METHOD_H 1
 
 #include "internal.h"
+#include "internal/imemo.h"
+#include "internal/compilers.h"
+#include "internal/static_assert.h"
 
 #ifndef END_OF_ENUMERATION
 # if defined(__GNUC__) &&! defined(__STRICT_ANSI__)