When we see a 'template' disambiguator that marks the next identifier

When we see a 'template' disambiguator that marks the next identifier
(or operator-function-id) as a template, but the context is actually
non-dependent or the current instantiation, allow us to use knowledge
of what kind of template it is, e.g., type template vs. function
template, for further syntactic disambiguation. This allows us to
parse properly in the presence of stray "template" keywords, which is
necessary in C++0x and it's good recovery in C++98/03.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106167 91177308-0d34-0410-b5e6-96231b3b80d8