Removed option "-parse-ast-check" from clang driver. This is now implemented

Removed option "-parse-ast-check" from clang driver.  This is now implemented
using "-parse-ast -verify".

Updated all test cases (using a sed script) that invoked -parse-ast-check to
now use -parse-ast -verify.

Fixed a bug where using "-verify" instead of "-parse-ast-check" would not
correctly create the DiagClient needed to accumulate diagnostics.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@42365 91177308-0d34-0410-b5e6-96231b3b80d8