Add DumpMocks_EnableDumpStartStackOverflowSimulation()

This mock function tells the CrashDebug_DumpStart() mock to set the
first word of g_crashCatcherStack to 0.  This simulates an overwrite of
the bottom of the stack as would happen during a stack overflow.
Make sure that stack doesn't overflow

CrashCatcher uses its own stack when creating a crash dump.  There is
a risk that this dedicated stack is too small (currently set to 1k).
This commit adds a simple overflow check which sets the bottom word of
the stack to 0xACCE55ED at the beginning of the core CrashCatcher loop
and then makes sure that it still has the same value at the end of each
loop iteration.

If an overflow is detected, an extra 4 bytes of ACCE55ED are appended
to the crash dump.
Make stack overflow message easier to read

Previously I was dumping 0xACCE55ED as a word but due to little endian
the bytes in the dump aren't as obvious.  I switched to using a byte
array for this value instead so that it would be more obvious when
looking at a hex representation of a dump whether a stack overflow
has been detected.