When building source location information for an _Atomic type, be sure

to fill in the source locations for the underlying value type. Fixes
an intermittent crasher (due to uninitialized data) in the PCH test
for _Atomic types.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@141512 91177308-0d34-0410-b5e6-96231b3b80d8