PR16243: Use CXXThisOverride during template instantiation, and fix up the
places which weren't setting it up properly. This allows us to get the right
cv-qualifiers for 'this' when it appears outside a method body in a class
template.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183483 91177308-0d34-0410-b5e6-96231b3b80d8