-Wcast-qual differently, by instead changing the signatore of those
"functions" to take a "volatile struct timeval*" instead of a
"struct timeval*". Many places, these functions are called with
&time, and time is declared as volatile in <sys/kernel.h>. This
way we can get rid of all the ugly casts which now also triggered
warnings, and caused more code to be added to work around the
problem.
Reviewed by thorpej.
