Delete dead code.

This is always overwritten by the one in NaClTargetInfo.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197346 91177308-0d34-0410-b5e6-96231b3b80d8
Add tests for all DescriptionString in Targets.cpp.

These right now just test that the same string is present in two files, but will
become more useful as clang's handling of DataLayout is refactored.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197347 91177308-0d34-0410-b5e6-96231b3b80d8