move token paste poisoning diagnostics to after the instantiation loc
for a token is set, this makes the diagnostic "expanded from stack" work
for this diagnostic.  Add a testcase for PR3918.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69544 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed