Bug #:

Submitted by:
Reviewed by:
Refactored code that deals with float/complex conversions (the previous commit).

- Removed 6 predicates that identify the built-in float/complex types.
- Added two helper functions GetFloatingRank() & ConvertFloatingRankToComplexType().
At present, these are static functions in SemaExpr.cpp. Conceptually, they would be nice
to move to Type, however there are layering problems with that (i.e. no ASTContext).
Another possibility is to move them to ASTContext?
- Simplified the logic in UsualArithmeticConversions() considerably.

llvm-svn: 39413