Ad-hoc fix for ambiguous type overloading
Ignore unrecognized intrinsic
Fix return type seeding.
- Introduce implicit cast ir node
Add test for invalid return type forcing
Use asymmetric resolution to resolve function call if we have mulitple possible candidates
Merge branch 'master' into fix_ambiguous_overloading

Conflicts:
	numba/typing/templates.py
Merge pull request #772 from sklam/fix_ambiguous_overloading

Fix ambiguous overloading, bad return type forcing