Fix stacktrace_from_exception builds with MinGW (#206)

Fixes #196

Author: apolukhin

src/from_exception.cpp

@@ -4,7 +4,7 @@
 // accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 
-#if defined(_MSC_VER)
+#if defined(__MINGW32__) || defined(_MSC_VER)
 
 #include <boost/stacktrace/safe_dump_to.hpp>
 #include <windows.h>