Fix --verbose option; add new --no-{silent|quiet|verbose} options.

Fix --verbose option; add new --no-{silent|quiet|verbose} options.

* libltdl/config/ltmain.m4sh (usage): Document
new options --no-silent/--no-quiet and --no-verbose.
(func_enable_tag): Handle new options.
Modified --verbose to actually activate opt_verbose.
New behavior: --silent disables both "normal" output and
func_verbose output.  --verbose enables both "normal"
output and func_verbose output. --no-silent enables
"normal" output, but does not affect func_verbose output.
--no-verbose disables func_verbose output, but does not
affect "normal" output.
* NEWS: announce new options --no-silent/--no-quiet, and
--no-verbose.
* doc/libtool.texi: document new options --no-silent/--no-quiet
and --no-verbose.