Add APIs on SBFunction and SBCompileUnit to inquire about the language type that the function/compile unit is defined in

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@222189 91177308-0d34-0410-b5e6-96231b3b80d8
Fix a problem where the StringPrinter could be mistaking an empty string for a read error, and reporting spurious 'unable to read data' messages. rdar://19007243

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@222190 91177308-0d34-0410-b5e6-96231b3b80d8