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, 2 insertions, 0 deletions

diff --git a/dln.c b/dln.c
index c40cbfc6ac..78c4c45a1f 100644
--- a/dln.c
+++ b/dln.c
@@ -1244,6 +1244,8 @@ rb_w32_check_imported(HMODULE ext, HMODULE mine)
 #endif
 
 #ifdef USE_DLN_DLOPEN
+# include "internal/stdbool.h"
+# include "internal/warnings.h"
 COMPILER_WARNING_PUSH
 #if defined(__clang__) || GCC_VERSION_SINCE(4, 2, 0)
 COMPILER_WARNING_IGNORED(-Wpedantic)