MinGW-w64 support

For now, SGC must be used, but `configure' does not select it
automatically.

Also, support Cygwin (in addition to MSYS) as a build environment
when using MinGW compilers. Since I build in a Cygwin environment
(which seemed to be the easiest way to get MinGW-w64 gcc), I use

  ../configure --host=x86_64-w64-mingw32 --enable-sgc

diff --git a/include/private/gcconfig.h b/include/private/gcconfig.h
index 5d8ab05f8f8d9692c7118047393adbe3363af6fe..d2a85c7bcecd49b91a955c0fb669ba0f52f49c04 100644 (file)
--- a/include/private/gcconfig.h
+++ b/include/private/gcconfig.h
@@ -433,7 +433,7 @@
 #   define CYGWIN32
 #   define mach_type_known
 # endif
-# if defined(__MINGW32__)
+# if defined(__MINGW32__) && !defined(_WIN64) /* PLTSCHEME: no _WIN64 */
 #   define I386
 #   define MSWIN32
 #   define mach_type_known