Add support for almost all Gen III games

The only Gen III game unsupported should be Pokémon LeafGreen v1.1
(Japan); as it is undumped.

A couple of bugs have also been fixed.

The code has also been refactored a little; now payload code goes into
`payload.c`. The codebase is also ready for a planned future change to
include savedata structure definitions. This will be done when it's done
-- PRs to help would be appreciated!

1 files changed, 13 insertions, 0 deletions

@@ -0,0 +1,13 @@
+        .text
+        .code 16
+
+        .global call_into_middle_of_titlescreen_func
+        .thumb_func
+call_into_middle_of_titlescreen_func:
+        push {lr}
+        push {r4-r5}
+        @ use r4 (which already got saved to the stack) as scratch space to reserve a variable amount of stack space
+        mov r4,sp
+        sub r4,r4,r1
+        mov sp,r4
+        bx r0
\ No newline at end of file