[VFS] Add "expand tilde" argument to getRealPath.

Add an optional argument to expand tildes in the path to mirror llvm's
implementation of the corresponding function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346453 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed