mesa: Add "OR COPYRIGHT HOLDERS" to license text disclaiming liability.

mesa: Add "OR COPYRIGHT HOLDERS" to license text disclaiming liability.

This brings the license text in line with the MIT License as published
on the Open Source Initiative website:

http://opensource.org/licenses/mit-license.php

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

This introduces some wrapping issues, to be fixed in the next commit.

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