Support mingw cross-compile

src/common/bit_set.h

@@ -16,7 +16,7 @@ namespace Common {
 
 // Helper functions:
 
-#ifdef _WIN32
+#ifdef _MSC_VER
 template <typename T>
 static inline int CountSetBits(T v) {
     // from https://graphics.stanford.edu/~seander/bithacks.html

src/common/logging/text_formatter.cpp

@@ -7,7 +7,7 @@
 
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
-#include <Windows.h>
+#include <windows.h>
 #endif
 
 #include "common/assert.h"

src/common/string_util.cpp

@@ -14,7 +14,7 @@
 
 #ifdef _WIN32
 #include <codecvt>
-#include <Windows.h>
+#include <windows.h>
 #include "common/common_funcs.h"
 #else
 #include <iconv.h>

src/common/thread.cpp

@@ -6,7 +6,7 @@
 #ifdef __APPLE__
 #include <mach/mach.h>
 #elif defined(_WIN32)
-#include <Windows.h>
+#include <windows.h>
 #else
 #if defined(__Bitrig__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__OpenBSD__)
 #include <pthread_np.h>

src/common/timer.cpp

@@ -4,7 +4,8 @@
 
 #include <time.h>
 #ifdef _WIN32
-#include <Windows.h>
+#include <windows.h>
+// windows.h needs to be included before other windows headers
 #include <mmsystem.h>
 #include <sys/timeb.h>
 #else