For more recent versions of msvc, the time_t type, as returned by
the time() function, is a 64-bit type. The srand() function, however,
expects an 'unsigned int' input parameter, leading to the warning.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Andreas Ericsson <ae@op5.se>