mv include/ruby/{impl,internal}

Devs do not love "impl".

include/ruby/internal/config.h

@@ -0,0 +1,131 @@
+#ifndef RBIMPL_CONFIG_H                              /*-*-C++-*-vi:se ft=cpp:*/
+#define RBIMPL_CONFIG_H
+/**
+ * @file
+ * @author     Ruby developers <ruby-core@ruby-lang.org>
+ * @copyright  This  file  is   a  part  of  the   programming  language  Ruby.
+ *             Permission  is hereby  granted,  to  either redistribute  and/or
+ *             modify this file, provided that  the conditions mentioned in the
+ *             file COPYING are met.  Consult the file for details.
+ * @warning    Symbols   prefixed  with   either  `RBIMPL`   or  `rbimpl`   are
+ *             implementation details.   Don't take  them as canon.  They could
+ *             rapidly appear then vanish.  The name (path) of this header file
+ *             is also an  implementation detail.  Do not expect  it to persist
+ *             at the place it is now.  Developers are free to move it anywhere
+ *             anytime at will.
+ * @note       To  ruby-core:  remember  that   this  header  can  be  possibly
+ *             recursively included  from extension  libraries written  in C++.
+ *             Do not  expect for  instance `__VA_ARGS__` is  always available.
+ *             We assume C99  for ruby itself but we don't  assume languages of
+ *             extension libraries. They could be written in C++98.
+ * @brief      Thin wrapper to ruby/config.h
+ */
+#include "ruby/config.h"
+
+#ifdef RUBY_EXTCONF_H
+# include RUBY_EXTCONF_H
+#endif
+
+#include "ruby/impl/compiler_since.h"
+
+#if defined(__cplusplus)
+#/* __builtin_choose_expr and __builtin_types_compatible aren't available
+# * on C++.  See https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html */
+# undef HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P
+# undef HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P
+
+# undef  HAVE_PROTOTYPES
+# define HAVE_PROTOTYPES 1
+
+# undef  HAVE_STDARG_PROTOTYPES
+# define HAVE_STDARG_PROTOTYPES 1
+
+/* HAVE_VA_ARGS_MACRO is for C.  C++ situations might be different. */
+# undef HAVE_VA_ARGS_MACRO
+# if __cplusplus >= 201103L
+#  define HAVE_VA_ARGS_MACRO
+# elif defined(__GXX_EXPERIMENTAL_CXX0X__) && __GXX_EXPERIMENTAL_CXX0X__
+#  define HAVE_VA_ARGS_MACRO
+# elif defined(__INTEL_CXX11_MODE__)
+#  define HAVE_VA_ARGS_MACRO
+# elif RBIMPL_COMPILER_SINCE(MSVC, 16, 0, 0)
+#  define HAVE_VA_ARGS_MACRO
+# else
+#  /* NG, not known. */
+# endif
+#endif
+
+#if RBIMPL_COMPILER_BEFORE(GCC, 4, 9, 0)
+# /* See https://bugs.ruby-lang.org/issues/14221 */
+# undef HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P
+#endif
+
+#if RBIMPL_COMPILER_BEFORE(GCC, 5, 0, 0)
+# /* GCC 4.9.2 reportedly has this feature  and is broken.  The function is not
+#  * officially documented below.  Seems we should not use it.
+#  * https://gcc.gnu.org/onlinedocs/gcc-4.9.4/gcc/Other-Builtins.html */
+# undef HAVE_BUILTIN___BUILTIN_ALLOCA_WITH_ALIGN
+#endif
+
+#ifndef STRINGIZE0
+# define STRINGIZE(expr) STRINGIZE0(expr)
+# define STRINGIZE0(expr) #expr
+#endif
+
+#ifdef AC_APPLE_UNIVERSAL_BUILD
+# undef WORDS_BIGENDIAN
+# ifdef __BIG_ENDIAN__
+#  define WORDS_BIGENDIAN
+# endif
+#endif
+
+#ifndef DLEXT_MAXLEN
+# define DLEXT_MAXLEN 4
+#endif
+
+#ifndef RUBY_PLATFORM
+# define RUBY_PLATFORM "unknown-unknown"
+#endif
+
+#ifdef UNALIGNED_WORD_ACCESS
+# /* Take that. */
+#elif defined(__i386)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(__i386__)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(_M_IX86)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(__x86_64)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(__x86_64__)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(_M_AMD64)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(__powerpc64__)
+# define UNALIGNED_WORD_ACCESS 1
+#elif defined(__mc68020__)
+# define UNALIGNED_WORD_ACCESS 1
+#else
+# define UNALIGNED_WORD_ACCESS 0
+#endif
+
+/* Detection of __VA_OPT__ */
+#if ! defined(HAVE_VA_ARGS_MACRO)
+# undef HAVE___VA_OPT__
+
+#else
+# /* Idea taken from: https://stackoverflow.com/a/48045656 */
+# define RBIMPL_TEST3(q, w, e, ...) e
+# define RBIMPL_TEST2(...)          RBIMPL_TEST3(__VA_OPT__(,),1,0,0)
+# define RBIMPL_TEST1()             RBIMPL_TEST2("ruby")
+# if RBIMPL_TEST1()
+#  define HAVE___VA_OPT__
+# else
+#  undef HAVE___VA_OPT__
+# endif
+# undef RBIMPL_TEST1
+# undef RBIMPL_TEST2
+# undef RBIMPL_TEST3
+#endif /* HAVE_VA_ARGS_MACRO */
+
+#endif /* RBIMPL_CONFIG_H */