mesa: Change "BRIAN PAUL" to "THE AUTHORS" in license text.

mesa: Change "BRIAN PAUL" to "THE AUTHORS" in license text.

Generated automatically be the following shell command:
$ git grep 'BRIAN PAUL BE LIABLE' | sed 's/:.*$//g' | xargs -I '{}' \
  sed -i 's/BRIAN PAUL/THE AUTHORS/' {}

The intention here is to protect all authors, not just Brian Paul.  I
believe that was already the sensible interpretation, but spelling it
out is probably better.

More practically, it also prevents people from accidentally copy &
pasting the license into a new file which says Brian is not liable when
he isn't even one of the authors.

Reviewed-by: Brian Paul <brianp@vmware.com>