Recommit r186217 with testcase fix:

 Use the function attributes to pass along the stack protector buffer size.

 Now that we have robust function attributes, don't use a command line option to
 specify the stack protecto buffer size.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186863 91177308-0d34-0410-b5e6-96231b3b80d8