Initializes everything on the stack (including padding)
with a specific debug value. This is intended to eliminate
all classes of uninitialized stack variable exploits and
information exposures, even variables that were warned about
having been left uninitialized.

Pattern initialization is known to provoke many existing bugs
related to uninitialized locals, e.g. pointers receive
non-NULL values, buffer sizes and indices are very big. The
pattern is situation-specific; Clang on 64-bit uses 0xAA
repeating for all types and padding except float and double
which use 0xFF repeating (-NaN). Clang on 32-bit uses 0xFF
repeating for all types and padding.