Force logs during enable hook

During the execution of enable hook the flag poormanscron_log_progress should be enabled, i.e. considering default to 1 only during module enable hook: variable_get('poormanscron_log_progress', 1)
afterwards it can be treated normally as variable_get('poormanscron_log_progress', 0)
or even better, do not consider the value of poormanscron_log_progress during enable hook and force logs during enable hook

the reason would be avoiding "the white screen of dead" or any other failure, since it will be very common that a site enabling poormanscron module hasn't run cron for a while, provoking the first poormanscron to execute while reloading admin/build/module page (as soon as got installed)
this results in a very confusing result when something goes wrong (not for poormanscron guilty, but for some cron hook provoking timeout)
for example #348994: Poormanscron hang
and there remains no record about what happened, making poormanscron look guilty when (perhaps) it isn't