Check if restrict keyword is supported

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66598 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.ac

@@ -1174,6 +1174,7 @@ AC_C_CHAR_UNSIGNED
 AC_C_INLINE
 AC_C_VOLATILE
 AC_C_TYPEOF
+AC_C_RESTRICT
 
 AS_CASE(":$ac_cv_c_const:$ac_cv_c_volatile:",
     [*:no:*], [AC_MSG_ERROR(ANSI C-conforming const and volatile are mandatory)])

win32/Makefile.sub

@@ -866,6 +866,11 @@ $(CONFIG_H): $(MKFILES) $(srcdir)/win32/Makefile.sub $(win_srcdir)/Makefile.sub
 #define RUBY_LONGJMP(env,val) longjmp(env,val)
 #define RUBY_JMP_BUF jmp_buf
 #define inline __inline
+!if $(MSC_VER) >= 1900
+#define restrict __restrict
+!else
+#define restrict /* not supported */
+!endif
 #define NEED_IO_SEEK_BETWEEN_RW 1
 !if "$(MACHINE)" == "x86" || "$(ARCH)" == "x64" || "$(ARCH)" == "ia64"
 #define STACK_GROW_DIRECTION -1