This fixes transcendentals and some other buggy instructions exposed by `ptx_tests` (abs, neg). Add (slow - hardware limitation) tanh.
Only two remaining incorrect instructions are div and sqrt with non-default rounding, but this commit is already bloated enough
Implements bar.red.and.pred and bar.red.or.pred, using the undocument __ockl_wgred functions. Doesn't yet add support for numbered barriers and threadcount, as these are not needed for llm.c.
