Substitute "licence" with "license".

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@1607 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

LEGAL

@@ -157,7 +157,7 @@ missing/strtoul.c:
 
 missing/vsnprintf.c:
 
-  This file is under the old-style BSD licence.  Note that the
+  This file is under the old-style BSD license.  Note that the
   paragraph 3 below is now null and void.
 
     Copyright (c) 1990, 1993
@@ -243,7 +243,7 @@ ext/socket/addrinfo.h:
 ext/socket/getaddrinfo.c:
 ext/socket/getnameinfo.c:
 
-  These files are under the BSD licence.
+  These files are under the BSD license.
 
     Copyright (C) 1995, 1996, 1997, 1998, and 1999 WIDE Project.
     All rights reserved.