Windows support: portable local server launch + clean quit, %APPDATA% data dir, Win32 libs, MinGW/MSVC build docs

server/Log.h

@@ -7,7 +7,10 @@
 
 namespace bs {
 
-#if defined(__GNUC__)
+// MinGW builds define __USE_MINGW_ANSI_STDIO (see CMakeLists.txt) so %zu works on old msvcrt.
+#if defined(__MINGW32__)
+__attribute__((format(gnu_printf, 1, 2)))
+#elif defined(__GNUC__)
 __attribute__((format(printf, 1, 2)))
 #endif
 inline void logf(const char* fmt, ...) {