Merge pull request #32 from mattn/mingw

Fix build for MinGW compiler
diff --git a/src/farmhash.cc b/src/farmhash.cc
index f2b99ff..9173ccd 100644
--- a/src/farmhash.cc
+++ b/src/farmhash.cc
@@ -114,7 +114,7 @@
 
 #if defined(FARMHASH_UNKNOWN_ENDIAN) || !defined(bswap_64)
 
-#ifdef _MSC_VER
+#ifdef _WIN32
 
 #undef bswap_32
 #undef bswap_64
@@ -225,7 +225,7 @@
   return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));
 }
 
-#if defined(_MSC_VER) && defined(FARMHASH_ROTR)
+#if defined(_WIN32) && defined(FARMHASH_ROTR)
 
 STATIC_INLINE uint32_t Rotate32(uint32_t val, int shift) {
   return sizeof(unsigned long) == sizeof(val) ?