Try a solution to drvtrb seg-fault on Pleiades: collectgarbage domain

The seg fault occurred after a crashed run.
Do some work on the PDF-machine

[squashed commits follow]

Speed up pdf-machine by caching mean, variance, etc

Add residual and integral calculations to pdf-machine

Change pdf-machine count type from int to uint64_t from stdint.h

Before the change, pdf-machine broke on greater than or equal to 512^3 *
16 = 2^31 counts. Now it should go up to 2^63 counts safely.

Fix bug with residual column, stop printing total counts of each hist

Fix pdf-machine Hopkins model so that P=0 when u<0