File missing from the dist tarball.

--- doc/Makefile.in.orig	Sat Jul 12 20:50:56 2014
+++ doc/Makefile.in	Sat Jul 12 20:51:08 2014
@@ -582,7 +582,6 @@ doc-install:
 	-$(INSTALL_DATA) $(top_srcdir)/CREDITS $(docdir)/
 	-$(INSTALL_DATA) $(top_srcdir)/README $(docdir)/
 	-$(INSTALL_DATA) $(top_srcdir)/README.MACOSX $(docdir)/
-	-$(INSTALL_DATA) $(top_srcdir)/README.PLUGIN $(docdir)/
 	-$(INSTALL_DATA) $(top_srcdir)/INSTALL $(docdir)/
 
 install-data-hook:	doc-install