improve aggr_hits.cpp

[http://dummy.us.eu.org/robert (Robert)]

put compilation command line as a comment
put "find" run command line as a comment
make sure spam never exceeds 25% of the good
change global variables to local static
use non-empty prefix in lieu of expandinghits flag
separate out case of ']' from ',' in if-then-else
make cutting off of ';[0-9]+' more robust
initialize count to 1, not 0, for goodcountsdb and spamcountsdb
use -Wall when compiling
make expand_hits() create list of pointers to after each command to replace listify_hits()