added populateFPMBaseline()

Adds baseline function level optimization passes to the pass manager. To be
used with a Patmos build, when the clang frontend compiles bitcode for later
(link-time) optimization.
singlepath: fix unconditional initialisation

* in corner cases, when they'd be re-predicated by
  applyPredicates in an inner scope
singlepath: peephole optimization

* eliminate redundant loads/stores of R26
singlepath: deferred elimination of frame indices

* eases elimination of redundant loads/stores to stack slots