[Linux] Return as soon as there is an event
[Linux] Return as soon as there is an event

This could avoid overflowing the event queue. Or if the timeout is large
enought, Dispatch_Event could overflow the event queue (never seen this
happen, however).

giuliolunati/ren-c,codebybrett/ren-c,hostilefork/rebol,mbk/ren-c,rgchris/ren-c,draegtun/ren-c,kealist/ren-c,giuliolunati/ren-c,codebybrett/ren-c,kealist/ren-c,draegtun/ren-c,codebybrett/ren-c,draegtun/ren-c,codebybrett/ren-c,hostilefork/rebol,draegtun/ren-c,rgchris/ren-c,hostilefork/rebol,rgchris/ren-c,rgchris/ren-c,hostilefork/rebol,mbk/ren-c,kealist/ren-c,kealist/ren-c,mbk/ren-c,giuliolunati/ren-c,kealist/ren-c,draegtun/ren-c,giuliolunati/ren-c,hostilefork/rebol,kealist/ren-c,codebybrett/ren-c,codebybrett/ren-c,mbk/ren-c,hostilefork/rebol,giuliolunati/ren-c,rgchris/ren-c,draegtun/ren-c