Add -P to the documentation head.

This is a companion patch for 211dcac643
commit, to add the newly introduced -P option to the list of options.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-cvsimport.txt

@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 'git-cvsimport' [ -o <branch-for-HEAD> ] [ -h ] [ -v ]
 			[ -d <CVSROOT> ] [ -p <options-for-cvsps> ]
-			[ -C <git_repository> ] [ -i ] [ -k ]
+			[ -C <git_repository> ] [ -i ] [ -P <file> ] [ -k ]
 			[ -s <subst> ] [ -m ] [ -M regex ] [ <CVS_module> ]