The RSA Data Security, Inc. implementation license bears a requirement
similar to the old problematic BSD license with advertising clause.

Change-Id: I877b71ff0548934b1c4fd87245696f53dedbdf26

Change-Id: Ieebea089095d9073b3a94932791099f614ce120c

This renames the vpx_codec/ directory to vpx/, to allow applications
to more consistently reference these includes with the vpx/ prefix.
This allows the includes to be installed in /usr/local/include/vpx
rather than polluting the system includes directory with an
excessive number of includes.

Change-Id: I7b0652a20543d93f38f421c60b0bbccde4d61b4f