Add line between licenses in COPYING.

More clearly delineate which files are associated with each license.
diff --git a/COPYING b/COPYING
index 70b39cb..cd5fca1 100644
--- a/COPYING
+++ b/COPYING
@@ -28,6 +28,7 @@
 PERFORMANCE OF THIS SOFTWARE.
 
 
+--------------------------------------------------------------------------------
 fontconfig/fc-case/CaseFolding.txt
 
 © 2019 Unicode®, Inc.
@@ -35,6 +36,7 @@
 For terms of use, see http://www.unicode.org/terms_of_use.html
 
 
+--------------------------------------------------------------------------------
 fontconfig/src/fcatomic.h
 
 /*
@@ -69,6 +71,7 @@
  */
 
 
+--------------------------------------------------------------------------------
 fontconfig/src/fcfoundry.h
 
 /*
@@ -94,6 +97,7 @@
 */
 
 
+--------------------------------------------------------------------------------
 fontconfig/src/fcmd5.h
 
 /*
@@ -114,6 +118,7 @@
  */
 
 
+--------------------------------------------------------------------------------
 fontconfig/src/fcmutex.h
 
 /*
@@ -148,6 +153,7 @@
  */
 
 
+--------------------------------------------------------------------------------
 fontconfig/src/ftglue.[ch]
 
 /* ftglue.c: Glue code for compiling the OpenType code from