Added GNU Lesser General Public License version 2.1 blurb to Makefile

Copied from mce.h under assumption that the Makefile is covered by the same
license as the source code it is used to compile.

Makefile

@@ -2,6 +2,18 @@
 # Copyright © 2004-2011 Nokia Corporation.
 # Written by David Weinehall
 # Modified by Tuomo Tanskanen
+#
+# mce is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License
+# version 2.1 as published by the Free Software Foundation.
+#
+# mce 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 mce.  If not, see <http://www.gnu.org/licenses/>.
 
 VERSION := 1.12.5