Fix two cosmetic differences between our LGPL copy and the one from the FSF.

Plus replace one occurrence of "version 2 of the license" with "version 2.1
of the license", same as in the FSF version. This has always been LGPL 2.1.

Originally committed as revision 9609 to svn://svn.ffmpeg.org/ffmpeg/trunk

COPYING

@@ -476,7 +476,7 @@ convey the exclusion of warranty; and each file should have at least the
     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 2 of the License, or (at your option) any later version.
+    version 2.1 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
@@ -485,7 +485,7 @@ convey the exclusion of warranty; and each file should have at least the
 
     You should have received a copy of the GNU Lesser General Public
     License along with this library; if not, write to the Free Software
-    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
 Also add information on how to contact you by electronic and paper mail.