Enable Wbounded by default. Passing bound bigger than the buffer

Enable Wbounded by default.  Passing bound bigger than the buffer
size almost always has security implications.  I think this quote
from Theo summarizes the situation best:

Which is why it is important to have at least one unforgiving
platform in the ecosystem which properly labels shit shit.

That's OpenBSD.  If anyone can't handle that, they can go to platforms
which hide the reality.