Change ParseOptionalCXX0XVirtSpecifierSeq to take a VirtSpecifiers struct.

Enforce C++[class.mem]p8:
A virt-specifier-seq shall contain at most one of each virt-specifier.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123611 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed