Build dmake with mingw under msys

I have problem while configure dmake for mingw. Configure script doesn't correctly detect win platform. I attach patch for this issue

```
--- a/configure 2012-11-27 12:44:45 +0400
+++ b/configure 2012-11-27 12:12:26 +0400
@@ -4349,7 +4349,7 @@
OS_VERSION=cygwin
CASE_INSENSITIVE_FS=true
;;
- "MINGW")
+ MINGW*)
OS_VERSION=mingw
OS_TYPE=winnt
BUILDINFO="Windows / MinGW"
```
