parse.y: Change copyright header to refer to version 3 of the GNU General Public...

parse.y: Change copyright header to refer to version 3 of the GNU General Public...

* parse.y: Change copyright header to refer to version 3 of the GNU
  General Public License and to point readers at the COPYING3 file.
* lex.l: Likewise.
* lang.opt: Likewise.
* lang-specs.h: Likewise.
* treelang.h: Likewise.
* config-lang.in: Likewise.
* tree-convert.c: Likewise.
* treetree.c: Likewise.
* tree1.c: Likewise.
* Make-lang.in: Likewise.
* treetree.h: Likewise.
* spec.c: Likewise.

From-SVN: r126713