[$] O_MAYEXEC — explicitly opening files for execution

Normally, when a kernel developer shows up with a proposed option thatdoesn't do anything, a skeptical response can be expected. But there areexceptions. Mickael Salaun is proposingthe addition of a new flag (O_MAYEXEC) for the openat2() system call that, by default, will change nothing. But it doesopen a path toward tighter security in some situations.