Fix usage of timeval_ms()

Fix usage of timeval_ms()

First, fix the timeval_ms() implementation to not have K&R but ANSI
argument semantics by adding a missing void.

timeval_ms() returns an int64_t, not uint64_t or long long. Consistently
use int64_t for variables and PRI*64 as format string.

While at it, change a few related variables to bool for clarity.

Note that timeval_ms() may return a negative error code, but not a
single caller checks for that.

Change-Id: I27cf83e75b3e9a8913f6c43e98a281bea77aac13
Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-on: http://openocd.zylin.com/3499
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>