Move UTF conversion routines from clang/lib/Basic to llvm/lib/Support

This is required to use them in TableGen.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173924 91177308-0d34-0410-b5e6-96231b3b80d8
Index/special-html-characters.m: mark this as XFAIL for valgrind

Fix is being discussed on cfe-dev.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173925 91177308-0d34-0410-b5e6-96231b3b80d8
Revert unintended change


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173927 91177308-0d34-0410-b5e6-96231b3b80d8