Remove generation time from the header
Remove generation time from the header

Running "make prep" on a different day will generate different files
even when nothing really changed, and thus confuses the building system
for incremental building.

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