reviewed by deraadt@, tedu@

page after each page size allocation to detect overrun.  this is
somewhat electric fence like, while attempting to be mostly usable in
production.  also, use tdeval's chunk randomization code.
enabled with the G option.
ok deraadt and co.

actually an error, A still applies full effect.
suggested by phk. ok deraadt@ tdeval@

lock before setting malloc_func, not after.
ok cloder@ deraadt@

with error messages elsewhere.  requested ok deraadt@ henning@

ok deraadt@ henning@ millert@

ok tdeval@

- extend_pgdir and malloc_make_chunks return int, not void*
ok tedu@

ok tdeval@ henning@ millert@

Also fix a signed vs. unsigned issue while I am at it.
Found by Jim Geovedi.  OK deraadt@

STDERR_FILENO instead of 2.
OK millert@

OK deraadt@

to such, permitting them to be discovered, instead of exploited as the ssh
crc insertion detector was.  Idea by theo, written by tdeval.

(the code was already there, just not enabled).

their own malloc() implementation.

didn't do so for us.  By default, malloc() zeros out the space it
allocates but the programmer cannot rely on this as it is implementation-
specific (and configurable via /etc/malloc.conf)

All POSIX libc api now there (to P1003.1c/D10)
(more md stuff is needed for other libc/arch/*)
(setlogin is no longer a special syscall)
Add -pthread option to gcc (that makes it use -lc_r and -D_POSIX_THREADS).
Doc some re-entrant routines
Add libc_r to intro(3)
dig() uses some libc srcs and an extra -I was needed there.
Add more md stuff to libc_r.
Update includes for the pthreads api
Update libc_r TODO

This is one of many places in the source that have
#if defined("list all architectures")
Is there some possible way to eliminate, reduce these or at least
have a file that describes all occurrances so that when a new port is
done this could be addressed. like the recent hppa port, does it need to
take a look at this????

to an object of size zero. This will allow testing on reallocs return value
to determine if the operation was successful or not.

sizeof *pt -> sizeof *px (point to same type of struct but looked wrong).

output).

Reduce diffs wrt. FreeBSD some