Be smarter when parsing variable declarations with unknown types.

Specifically, avoid typo-correcting the variable name into a type before
typo-correcting the actual type name in the declaration. Doing so
results in a very unpleasant cascade of errors, with the typo correction
of the actual type name being buried in the middle.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@219732 91177308-0d34-0410-b5e6-96231b3b80d8