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.
err and warn are BSD format but they are not recommended by library
developers. However their consiseness is useful!
The solution is to use some macros that create xerr etc which then
just map to the error() function. The next problem is error() uses
program_invocation_name so we set this to program_invovation_short_name
This is a global set but seems to be the convention (or at least errors
are on the short name only) used everywhere else.
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.