gtb-probe.cpp: fix reentrancy bug in egtb_get_id(), which was causing assertions in multithreaded MultiPV mode. Patch submitted to Miguel Ballicora.
xcode: project cleanup
add gtb osx project (splitting lib out of the master project
remove gtb source from master project, now building/linking libgtb.a via subproject
bitcount: fix typo which was preventing POPCNT code from functioning properly