Improve 3 functions, match 1

[titus-ssbm]

Fixes four integer type declarations that caused MWCC to emit width and
signedness conversions that retail does not have.

When an argument is passed to a parameter narrower than itself, MWCC emits a
conversion at the call site (extsb, extsh, clrlwi). When the declared type
is wide enough, no conversion is emitted. Retail's codegen therefore pins the
width of each parameter: a plain register copy where we emit a mask means the
declaration is too narrow, and a mask where we emit a plain copy means it is too
wide. This is the s8-is-usually-an-int case described in CONTRIBUTING.

• gm_801B5324: arg1 widened to s32. The indirect call through x54 now
  narrows its first argument as retail does. Matches.
• fn_8016B388: arg1 widened to int, removing an extsh in the caller
  fn_801891F4 (99.517 -> 99.786).
• mn_80230D18: arg2 widened to int, removing an extsb in the caller
  mn_80230E38 (99.843 -> 99.961).
• ifStock_802F8298_get_flag: return type changed to u8. The getter and a
  later direct read of the same byte are one common subexpression, so the
  getter's int was carried into a comparison that retail performs unsigned
  (cmpwi -> cmplwi), improving ifStock_802F8298 (97.064 -> 97.191).

gm_801B5324 is the one case where s32 and int are not interchangeable: it
matches with s32 and regresses with int.

Claude Opus 5 did the function matching work.

[decomp-dev]

Report for GALE01 (3bf5523 - 88799d7)

📈 Matched code: 95.45% (+0.02%, +768 bytes)

✅ 1 new match

Unit	Item	Bytes	Before	After
main/melee/gm/gmallstar	gm_801B5324	+45	94.21%	100.00%

📈 3 improvements in unmatched items

Unit	Item	Bytes	Before	After
main/melee/gm/gm_1884	fn_801891F4	+6	99.52%	99.79%
main/melee/mn/mnmainrule	mn_80230E38	+3	99.84%	99.96%
main/melee/if/ifstock	ifStock_802F8298	+2	97.06%	97.19%

[MarkMcCaskey]

Nice!