Dropped a fair amount of reundant code in favour of the library code
in path.c

Added option --strict-paths with documentation, with backwards
compatibility for whitelist entries with symlinks.

Everything that worked earlier still works insofar as I have
remembered testing it.
Signed-off-by: NAndreas Ericsson <ae@op5.se>
Signed-off-by: NJunio C Hamano <junkio@cox.net>