vmem: implementation of vmem_check()

Validate pool consistency.
Detect: wrong data in header, not zeroed values inside zeroed pages,
data structures from outside of memory region, conflict memory region between pools.
The .match files seem to be full of these lines that do nothing but match a line with anything on it.  So basically you're counting lines.  That doesn't seem very useful and seems very fragile -- if someone adds another log line these tests mysteriously fail, and you're not actually checking that the thing you wanted the library to report is reported.  In other tests we grep for the log lines we're expecting, putting the output of grep into another file and using a match file on it.