[media] DocBook: Move all media docbook stuff into its own directory

This patch addresses several issues pointed by Randy Dunlap
<rdunlap@xenotime.net> at changeset ece722c:

- In the generated index.html file, "media" is listed first, but it
  should be listed in alphabetical order, not first.

- The generated files are (hidden) in .tmpmedia/

- The link from the top-level index.html file to "media" is to
  media/index.html, but the file is actually in .tmpmedia/media/index.html

- Please build docs with and without using "O=builddir" and test that.

- Would it be possible for media to have its own Makefile instead of
  merging into this one?

Due to the way cleandocs target works, I had to rename the media DocBook
to media_api, otherwise cleandocs would remove the /media directory.

Thanks-to: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/Documentation/DocBook/.gitignore b/Documentation/DocBook/.gitignore
index 679034c..2c8c882 100644
--- a/Documentation/DocBook/.gitignore
+++ b/Documentation/DocBook/.gitignore
@@ -8,4 +8,13 @@
 *.dvi
 *.log
 *.out
-media/
+crop.gif
+dvbstb.png
+fieldseq_bt.gif
+fieldseq_tb.gif
+media-indices.tmpl
+nv12mt.gif
+nv12mt_example.gif
+vbi_525.gif
+vbi_625.gif
+vbi_hsync.gif