win32: move _USE_MATH_DEFINES before includes to ensure M_PI is defined

Author: Marcus Groeber

examples/tts/tts.cpp

@@ -1,11 +1,11 @@
+#define _USE_MATH_DEFINES // For M_PI on MSVC
+
 #include "arg.h"
 #include "common.h"
 #include "sampling.h"
 #include "log.h"
 #include "llama.h"
 
-#define _USE_MATH_DEFINES // For M_PI on MSVC
-
 #include <algorithm>
 #include <cmath>
 #include <cstdio>