Fix assertion failure if we can't deduce a template argument for a variable

template partial specialization.

In passing, fix the deduction-crash.cpp test to actually run all the tests. Due
to a typo, the last third of the file was being skipped by the parser and some
of the tests were not actually testing anything as a result. Switch from
FileCheck to -verify to make the problem more obvious and prevent this
happening again.

llvm-svn: 304604