Inspired by the cvs annotate documentation improve and expand the man page
to also mention the limitations of file annotations. Since people coming
from the SVN/CVS world might first look here, also briefly advertise how
the pickaxe interface makes it easy to go beyond these limitation.
Signed-off-by: Jonas Fonseca <fonseca@diku.dk> Signed-off-by: Junio C Hamano <junkio@cox.net>