Documentation: replace some non-ASCII characters by equivalent markup


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172917 91177308-0d34-0410-b5e6-96231b3b80d8
Documentation: remove more mentions of Tcl

Followup for r172836


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172918 91177308-0d34-0410-b5e6-96231b3b80d8