Rename legal.txt to LEGAL.txt

Author: Cube

legal.txt LEGAL.txtlegal.txt renamed to LEGAL.txt

@@ -1036,4 +1036,4 @@ Code generated by the Protocol Buffer compiler is owned by the owner
 of the input file used when generating it.  This code is not
 standalone and requires a support library to be linked with it.  This
 support library is itself covered by the above license.
-===================================================================================
+===================================================================================