wmake : set WM_NCOMPPROCS automatically when both WM_HOSTS and WM_SCHEDULER are set

This substantially eases enabling/disabling distributed compiling
For example,
 - export WM_HOSTS="host1:N ... hostN:N"  as usual
 - simply set/unset WM_SCHEDULER

etc/aliases.{sh,csh} added aliases for enabling/disabling wmakeScheduler
 - alias wmSchedON='export WM_SCHEDULER=$WM_PROJECT_DIR/wmake/wmakeScheduler'
 - alias wmSchedOFF='unset WM_SCHEDULER'

Removed wmakeLockScheduler, identical to wmakeScheduler except a 'sleep'