loongarch: Add SLJIT_UPPER_BITS_SIGN_EXTENDED (#276) #52

Job	Run time
build-test-on-loongarch64	1m 50s
build-test-on-armt2	2m 1s
build-test-on-aarch64	1m 33s
build-test-on-riscv32	2m 23s
build-test-on-riscv32-extensions	2m 7s
build-test-on-riscv64	2m 10s
build-test-on-riscv64-extensions	2m 52s
build-test-on-s390x	2m 0s
build-test-on-arm32	1m 55s
build-test-on-x64	18s
build-test-on-x86	25s
	19m 34s

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