Rename COPYING.txt to LICENSE for opensource compliance and update links
in README.txt.
diff --git a/Makefile.am b/Makefile.am
index 790b8f7..09b92ea 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -40,7 +40,7 @@
   generate_descriptor_proto.sh                                               \
   README.txt                                                                 \
   INSTALL.txt                                                                \
-  COPYING.txt                                                                \
+  LICENSE                                                                    \
   CONTRIBUTORS.txt                                                           \
   CHANGES.txt                                                                \
   editors/README.txt                                                         \