- fix showpage1 only decrementing proc counter once limit is reached;
this blocked having more than one loadpages process after NPROC calls,
since the next one has to wait until the last has exited
- allow procs to skip pages currently being loaded by others; this
forced processes to wait for each other at the same page
- bump NPROC from 4 to 8
- (hack) immediately fork a few times after adding all pages at
startup to force loading a batch of pages in parallel
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