This adds a hacked version of simple-shm which can create multiple
pointer and keyboard resources. The resources are created with the
command line options -p and -k. Both take an integer argument which
specifies the time in seconds after the program is started when the
resource should be created. It can also take a second time with a
colon separator to specify when the resource should be released.

For example:

 weston-multi-resource -p5 -p7 -k9 -p12:14

That would create a pointer after 5 seconds, a second pointer 2
seconds later, a keyboard 2 seconds after that, a third pointer after
a further 3 seconds and finally after 2 more seconds it would release
that final pointer resource.

This can be used along with WAYLAND_DEBUG to check that it gets the
right events for example if the pointer is created while the client's
surface already has focus and so on.