Signed-off-by: NPavel Roskin <proski@gnu.org>

Remove inneeded system includes.

Most system includes are not needed.  In particular, the hardware
backends don't need anything network related.  Some includes have been
moved from local headers to the C files where they are actually used.
Includes that have to be in the local headers are no longer from the C
sources.
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>