Remove remaining GPL reference in src/CMakeLists.txt.

  - License is LGPL.

src/CMakeLists.txt

 # Copyright (C) 2010 Florent Lamiraux, Thomas Moulard, JRL, CNRS/AIST.
 #
 # This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
+# it under the terms of the GNU Lesser General Public License as published by
 # the Free Software Foundation, either version 3 of the License, or
 # (at your option) any later version.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
+# GNU Lesser General Public License for more details.
 #
-# You should have received a copy of the GNU General Public License
+# You should have received a copy of the GNU Lesser General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 # Check for unistd.h presence.