time_stats.cpp

    start only enough jobs to fill CPUs per project,
    not all the CPU jobs at once.
    I'm not sure how much difference this makes,
    but this is how it's supposed to work.
- client: if app_info.xml doesn't specify flops,
    use an estimate that takes GPUs into account.
- client: if it's been more than 2 weeks since time stats update,
    don't decay on_frac at all.

svn path=/trunk/boinc/; revision=19035