[amd64] Fast OP_LREM_IMM for power of two operands.

This was the reason for one of our bad performance results in the
paper "Clash of the Lambdas" by Biboudis, Palladinos, Smaragdakis:

http://cgi.di.uoa.gr/~biboudis/clashofthelambdas.pdf
Merge pull request #1126 from schani/feature-fast-lrem-imm

[amd64] Fast OP_LREM_IMM for power of two operands.