procps automake defines restrict which means the binaries for procps
binaries compile. However external programs may not of defined
restrict which means they will not complie if they include files found
in /usr/include/proc.
Includes from libc6 use __restrict and if is good enough for
them, its good enough for us.
A callback provision in the form of xalloc_err_handler
(of type message_fn) was added to the alloc module.
This change allowed a program like top, who alters the
termios structure, to override the default fprint(stderr...)
behavior in the event of an error.
The new function xstrdup was also added for symmetry.
