[jit] Portably decompose power-of-two OP_[IL]REM_IMM.

Instead of generating a sequence of AMD64 instructions for
power-of-two OP_[IL]REM_IMM, portably decompose them to intermediate
code.

OP_IREM_IMM is decomposed on 32 and 64 bit archs, OP_LREM_IMM only on
64 bit archs.
Merge pull request #1131 from schani/feature-portable-fast-lrem-imm

[jit] Portably decompose power-of-two OP_[IL]REM_IMM.