rework logging to be more optimised, and some minor improvements.

removed function definitions and opted for using macros instead.
It now does not have a set limit when it comes to printing (at least,
it's the stdc's limit again). However, it is now no longer possible to
use a character pointer to print information to the screen.

src/io/shader.c

@@ -4,6 +4,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <stdio.h>
 
 #include "../error.h"