Handle all TemplateArguments in trivial TypeLocs.

Armed with a much better understanding of what
TemplateSpecializationTypeLoc::initializeArgLocs actually does, I now
understand that it's fine to just use an empty TemplateArgumentLocInfo
for Integral, Declaration, and NullPtr TemplateArguments.

Fixes PR14281. (The testcases are actually derived from libcxx_test in
deduction-crash.cpp because the original testcase was impossible to reduce.)