Fix heap corruption in malloc

Use SDL's malloc functions in abstractions.

src/packages/stdinc/IZ_stdlib.c

@@ -1,13 +1,13 @@
 #include "IZ_stdlib.h"
 
 void* IZ_malloc(size_t size) {
-	return malloc(size);
+	return SDL_malloc(size);
 }
 
 void* IZ_calloc(unsigned int count, size_t size) {
-	return calloc(count, size);
+	return SDL_calloc(count, size);
 }
 
 void IZ_free(void* p) {
-	free(p);
+	SDL_free(p);
 }

src/packages/stdinc/IZ_stdlib.h

@@ -1,7 +1,7 @@
 #ifndef IZ_STDLIB_H
 #define IZ_STDLIB_H
 
-#include <stdlib.h>
+#include <SDL_stdinc.h>
 
 void* IZ_malloc(size_t);
 void* IZ_calloc(unsigned int, size_t);