Revert [mangle] Fix mangling where an extra mangle context is required.

This reverts r374200 (git commit fd18e94697c987d5f24e25aa4e27adaffff3cce4)

Causes crashes just compiling `int main() {}` on my machine.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@374268 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed