Change __MINGW to __MINGW32__.  Patch submitted by Henrik Bach.

llvm-svn: 20243
diff --git a/llvm/lib/System/Win32/Process.inc b/llvm/lib/System/Win32/Process.inc
index 7c8de64..a47ff2e 100644
--- a/llvm/lib/System/Win32/Process.inc
+++ b/llvm/lib/System/Win32/Process.inc
@@ -23,7 +23,7 @@
 //===          and must not be UNIX code
 //===----------------------------------------------------------------------===//
 
-#ifdef __MINGW
+#ifdef __MINGW32__
 // This ban should be lifted when MinGW 1.0+ has defined this value.
 #  define _HEAPOK (-2)
 #endif