csearch: make -verbose print the number of filenames matched by -f regexp
csearch: make -verbose print the number of filenames matched by -f regexp

csearch already prints the trigrams and number of files matched from
the index if -verbose mode is on.

This patch preprocesses the list of fileids so we can print how many
were matched by the filename regex.

Fixes issue 14

R=rsc
http://codereview.appspot.com/6050057

magus424/codesearch,magus424/codesearch,salsifis/codesearch,junkblocker/codesearch,junkblocker/codesearch,salsifis/codesearch