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

junkblocker/codesearch,spuranam/codesearch,jmurzy/codesearch,chrsmithdemos/codesearch,kakaiu/codesearch,jmurzy/codesearch,rjpower/codesearch,StephanieMak/codesearch,wiless/codesearch,Tilka/codesearch,vrajanap/codesearch,mattn/codesearch,spuranam/codesearch,MARFMS/codesearch,CarlosGtrz/codesearch,mattn/codesearch,LiJiefei/codesearch,Tilka/codesearch,junkblocker/codesearch,google/codesearch,MARFMS/codesearch,wiless/codesearch,rjpower/codesearch,a5b/codesearch,google/codesearch,LiJiefei/codesearch,ancientlore/codesearch,ksmaheshkumar/codesearch,CarlosGtrz/codesearch,salsifis/codesearch,StephanieMak/codesearch,salsifis/codesearch,chrsmithdemos/codesearch,vrajanap/codesearch,ksmaheshkumar/codesearch,kakaiu/codesearch,a5b/codesearch,ancientlore/codesearch