mprotect PROT_SIGNAL

we'd like an mprotect PROT_SIGNAL flag for a compiler we're making

PROT_SIGNAL - marks the pages as unmapped while running signal handlers

this would be very useful, do you think you could provide it?

(not much more to say about it, it's supposed to do what it says on the tin, we want to unmap pages in signal handlers so as to catch bugs without causing memory corruption.)