Add missing logic for some 48-bit libcalls #18

Job	Run time
build-llvm (ubuntu-20.04, Release)	36m 34s
build-llvm (ubuntu-latest, Release)	39m 59s
build-llvm (macos-13, Release)	52m 48s
build-llvm (macos-14, Release)	20m 49s
build-clang (ubuntu-20.04, Release)	35m 5s
test-llvm	0s
build-clang (ubuntu-latest, Release)	36m 48s
test-llvm-z80 (ubuntu-20.04, Release)	2m 6s
build-clang (macos-13, Release)	37m 57s
test-llvm-z80 (ubuntu-latest, Release)	2m 6s
test-llvm-z80 (macos-13, Release)	3m 35s
test-llvm-z80 (macos-14, Release)	1m 57s
build-clang (macos-14, Release)	18m 21s
nightly	0s
test-clang	0s
	4h 48m 5s

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