Use 64-bit time_t

GLib's struct GTimeVal declares tv_sec as glong (will break around 2038).
Our struct timeval declares tv_sec as time_t...
warning: passing argument 1 of 'ctime' from incompatible pointer type
Taken from:
http://anoncvs.estpak.ee/cgi-bin/cgit/openbsd-ports/tree/sysutils/consolekit/patches/patch-tools_ck-history_c