Update license text

src/ADC.cpp

+/*
+ * Original File adc-dac-printf.c modified by Lisa Dreier, Margit Haspel and Werner Sembach
+ *
+ * Original License Header:
+ *
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2013 Karl Palsson <karlp@tweak.net.au>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * 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 library 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 Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
 #include "ADC.h"
 
 #include <libopencm3/stm32/adc.h>