[scan-build] fix xcode version parsing to handle dot releases.  Fixes <rdar://problem/13265300>.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@175781 91177308-0d34-0410-b5e6-96231b3b80d8
Try to get buildbots to pass these tests.

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@175784 91177308-0d34-0410-b5e6-96231b3b80d8