Tweak the partial ordering rules for function templates to prefer a

Tweak the partial ordering rules for function templates to prefer a
non-variadic function template over a variadic one. This matches GCC
and the intent of the C++0x wording, in a way that I think is likely
to be acceptable to the committee.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123581 91177308-0d34-0410-b5e6-96231b3b80d8