Re-apply r159875 with fixes.

- Split pedantic driver flag test into separate test file, and XFAIL on cygwin,mingw32
- Fix bug in tablegen logic where a missing '{' caused errors to be included in -Wpedantic.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159892 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed