Fixing Doxygen warnings in cpp11-migrate

Turned on doxygen warnings and fixed the resulting problems.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176712 91177308-0d34-0410-b5e6-96231b3b80d8
Removing 'modindex' from clang-tools-extra doc index

There are no python modules in clang-tools-extra so a link to this
auto-generated page, which currently isn't generated anyway, is not necessary.



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@176713 91177308-0d34-0410-b5e6-96231b3b80d8