1- wrc.h now includes syscon.h. This is a prerequisite to a non-inline
implementation of usleep (the current inline one is just a random
loop, 10x wrong on the spec). Without this we should modify sockitowm
where it calls usleep, but I'd better not touch sockitowm.

2- syscon.h includes <sys/types.h>.  This is needed to have
useconds_t.  I'd better have usleep take unsigned long, but some file
already includes sys/types.h, so our prototype must match that one.
Signed-off-by: Alessandro Rubini <rubini@gnudd.com>