singlepath: uncond. execute return-info instrs

instructions that store/restore return information need to be executed
unconditionally.
singlepath: remove sp-root attribute from cloned roots
singlepath: execute frame setup unconditionally

* fixed bug in predication of already predicated instructions
* using btest with immediate for loading predicates from slots
Merge branch 'master' of ssh+git://github.com/t-crest/patmos-llvm