Fix a crash bug when comparing overload quality of conversion operators with...

Fix a crash bug when comparing overload quality of conversion operators with conversion constructors.
Remove an atrocious amount of trailing whitespace in the overloaded operator mangler. Sorry, couldn't help myself.
Change the DeclType parameter of Sema::CheckReferenceInit to be passed by value instead of reference. It wasn't changed anywhere.
Let the parser handle C++'s irregular grammar around assignment-expression and conditional-expression.
And finally, the reason for all this stuff: implement C++ semantics for the conditional operator. The implementation is complete except for determining lvalueness.

llvm-svn: 69299