When modifying an implicit instantiation with information from an explicit one, make sure to reset the "right brace" location.

Otherwise the source range of the explicit instantiation may become invalid (begin location will be after the end location).

rdar://13706991

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@180070 91177308-0d34-0410-b5e6-96231b3b80d8