Add new mbmi and mbmi2 compiler flags
This adds support for the bit deposit and extraction operations provided by the BMI and BMI2 instruction set extensions on modern amd64 machines. Test Plan: Validate Reviewers: austin, simonmar, bgamari, hvr, goldfire, erikd Reviewed By: bgamari Subscribers: goldfire, erikd, trommler, newhoggy, rwbarton, thomie GHC Trac Issues: #14206 Differential Revision: https://phabricator.haskell.org/D4063