Fix fallout from r219557

Summary:
Consider the following nifty 1 liner: (0 ? csqrtl(2.0f) : sqrtl(2.0f)). One can easily obtain such code from e.g. tgmath. Right now it produces an assertion because we fail to do the promotion real => _Complex real.

The case was properly handled previously (old handleOtherComplexFloatConversion routine), but was forgotten in the current version. This seems to be about fallout from r219557

Reviewers: chandlerc, rsmith

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D6217