add missing GPL license

sphear_bf_power.m

@@ -14,8 +14,21 @@
 %% currently hardwired into this file, this needs to be fixed and turned into
 %% input parameters
 %%
-%% Copyright Fernando Lopez-Lezcano 2016
-%% 
+%% Copyright 2016, Fernando Lopez-Lezcano, All Rights Reserved
+%% nando@ccrma.stanford.edu
+%%
+%%  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
+%%  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.
+%%
+%%  You should have received a copy of the GNU General Public License
+%%  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 function [B] = sphear_bf_power(fmin, fmax, N, Fs, plotz)
   pkg load signal;