Restored missing Int to Integer conversion codegens
Regression test for StrLen.
Merge branch 'restored-itnative-codegen' of https://github.com/Ralith/Idris-dev into StrLen
Merge branch 'StrLen' of https://github.com/JanBessai/Idris-dev into StrLen
Use zext, because the length of a string is always positive