Reduce the number of builtin operator overload candidates added in certain

cases. First, omit all builtin overloads when no non-record type is in the set
of candidate types. Second, avoid arithmetic type overloads for non-arithmetic
or enumeral types (counting vector types as arithmetic due to Clang
extensions). When heavily using constructs such as STL's '<<' based stream
logging, this can have a significant impact. One logging-heavy test case's
compile time dropped by 10% with this. Self-host shows 1-2% improvement in
compile time, but that's likely in the noise.

llvm-svn: 121665