GBA: Place functions/variables in iwram

Placing functions and variables in iwram will *seriously* speed up your program. You only have limited amounts on the other hand (32K). I made the following defines based on The Dev'rs GBA Dev FAQs.

Defines:

#define IWRAM_FUNCTION __attribute__((section (".iwram"), long_call))
#define IWRAM_VARIABLE __attribute__((section (".iwram")))

Usage:

const int somearray[] IWRAM_VARIABLE = { ... }
void IWRAM_FUNCTION SomeFunction( ... ) { ... }

I figured out that there's some more info on this over at tonc after I posted.