[stackprotector] Implement the sspstrong rules for stack layout.

This changes the PrologueEpilogInserter and LocalStackSlotAllocation passes to
follow the extended stack layout rules for sspstrong and sspreq.

The sspstrong layout rules are:

1. Large arrays and structures containing large arrays (>= ssp-buffer-size)

are closest to the stack protector.

2. Small arrays and structures containing small arrays (< ssp-buffer-size) are

2nd closest to the protector.

3. Variables that have had their address taken are 3rd closest to the

protector.

Differential Revision: http://llvm-reviews.chandlerc.com/D2546