Cleanup tags usage and update commandline examples.

credits to: Violet Lin (from Google Code-in)
Signed-off-by: burek <burek021@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

This helps callers to intelligently switch between bitrate
variants.
Signed-off-by: Martin Storsjö <martin@martin.st>

Signed-off-by: Martin Storsjö <martin@martin.st>

This reverts commit f8a45fa1.

Conflicts:

	doc/optimization.txt

unless it stands for ffmpeg the program or is historic

Signed-off-by: Mans Rullgard <mans@mansr.com>
(cherry picked from commit 10ed96c7)

Signed-off-by: Mans Rullgard <mans@mansr.com>

Originally committed as revision 26283 to svn://svn.ffmpeg.org/ffmpeg/trunk

Originally committed as revision 26282 to svn://svn.ffmpeg.org/ffmpeg/trunk