ldconfig: remove ignored -v (verbose) option

The -v option used to print useful information when operating on a.out
format libraries. After the removal of a.out support, it was accepted
but did not have any effect.

Remove the option and update the man-page.

While here mention the set of historic options that are accepted but
ignored: "-elf", "-s", and "-v".

The FILES section contained outdated information and did not mention
the way library directories of optional ports and packages are
included in the library search path recorded in the hints file.

The description of the "-B" option was incorrect (described a planned
change) for big-endian platforms (powerpc64). These do still default
to big-endian hints files, since the current version of the "pkg"
program expects the hints file to be in native byte-order.

Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D44139