[autoconf] Fix 80+ and quoting.

Additional quoting for safety and satisfying newer autotools.  Fix a couple of 80 column violations.

http://llvm-reviews.chandlerc.com/D333



Signed-off-by: Saleem Abdulrasool <compnerd@compnerd.org>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173877 91177308-0d34-0410-b5e6-96231b3b80d8