Cleaned up function declarations, and fixed C compliance.

main.c

@@ -0,0 +1,11 @@
+#define HANDMADE_MATH_IMPLEMENTATION
+#include "HandmadeMath.h"
+
+int
+main(void)
+{
+    v2 VecOne = Vec2(1.0f, 1.0f);
+    v2 VecTwo = Vec2(3.0f, 3.0f);
+
+    v2 Result = AddVec2(VecOne, VecTwo);
+}