CHROMIUM: x86: need compat version of sys_prctl

CHROMIUM: x86: need compat version of sys_prctl

Since PR_SET_PTRACER_ANY is the equvalent of (unsigned long)-1, it
needs to be sign extended for 32-bit compat.

Powerpc was the only arch that did any kind of compat handling for prctl,
so move that code to generic location and add the PR_SET_PTRACER check
as needed for the yama module.

BUG=chromium-os:33531
TEST=run security_ptraceRestrictions

Change-Id: I2c034025de8d71b5c317318cee2e079a38461e6d
Signed-off-by: Olof Johansson <olofj@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/30672
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>