[allegro4.2] exec stack marking

[Markus Wichmann <markuswichmann89@gmail.com>]

Hi there,

I stumbled across this kind-of bug today: liballeg4.2 comes with an
executable stack marking on amd64. The culprit in the source is
src/amd64/acpus.s, but that is the only assembly file used for amd64.
You may want to add the lines

#if defined(__linux__) && defined(__ELF__)
.section .note.GNU-stack,"",%progbits
#endif

to all the assembly files. allegro doesn't appear to need an executable
stack, so there's just an unnecessary security risk.

I'm sending this patch to you because I couldn't find an upstream to
send it to.

Regards,
Markus Wichmann