Mostly revert 0.9.4.84, since it doesn't compile at all on modern
Linux systems (see sbcl-devel message by "Dave" on 2005-09-23):
* The decision of whether to use personality() should be completely
a run-time property, not a compile-time one.
* Change LISP_FEATURE_LINUX cpp conditionals back to LISP_FEATURE_X86
or remove them entirely (this is in linux-os.c, so LISP_FEATURE_LINUX
had better be defined; randomization is only enabled on x86 so
it's pointless to include the code on other platforms)
* To solve the problem that 0.9.4.84 was trying to address
(no <sys/personality.h> on versions of glibc more than three years
old) define the prototype of personality() in linux-os.c. This
might not be the optimal solution, but I suppose this isn't the
right time to experiment...
The syscall itself is old (goes at least back to kernel 2.0),
so the system call wrapper should exist even on old versions
of libc. There should thus be no problems with linking this
code even on ancient systems.