Review libc dependencies and remove when possible

Just for clarification, no plans to remove libc dependency, just did some code analysis to see how much raylib depend on stardard C library. My conclusions:

 - stdlib.h: primary dependency is for malloc() and free()
 - stdio.h: primary dependency is for FILE access, maybe it could go through a custom ABI?
 - string.h: just around 8 functions required
 - math.h: just around 8 functions required
 - others: 1-2 functions required for some other headers

src/raymath.h

@@ -135,7 +135,7 @@
 typedef struct float3 { float v[3]; } float3;
 typedef struct float16 { float v[16]; } float16;
 
-#include <math.h>       // Required for: sinf(), cosf(), tan(), fabs()
+#include <math.h>       // Required for: sinf(), cosf(), sqrtf(), tan(), fabs()
 
 //----------------------------------------------------------------------------------
 // Module Functions Definition - Utils math