Define sethostname on platforms that do not provide the declaration.
Provide a function for platforms that lack it. The general handling
of the provided function is to simply return -1 and set errno to
ENOSYS. A specific handler is provided for Minix.
* lib/sethostname.c (sethostname): New file. Provide sethostname
for systems that lack it.
* m4/sethostname.m4 (gl_FUNC_SETHOSTNAME): New file. Detection of
sethostname declaration and function.
* modules/sethostname: New file. Define the sethostname module.
Signed-off-by: Ben Walton <bwalton@artsci.utoronto.ca>