gba

added foundation for multiply long #29

Job	Run time
build	5m 32s
test (ldrsb_ldrsh)	12m 2s
test (ldr_str_immediate_offset)	12m 21s
test (ldm_stm)	14m 20s
test (data_proc_register_shift)	11m 48s
test (data_proc_immediate)	11m 33s
test (ldr_str_register_offset)	12m 6s
test (data_proc_immediate_shift)	11m 42s
test (b_bl)	17m 34s
test (mul_mla)	23m 43s
test (swi)	15m 51s
test (ldrh_strh)	11m 1s
	2h 39m 33s

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