Don't try to generate HTML manual

The HTML manual is missing from the 2.2.11 tarball, so the doc build
tries to generate it, but MacPorts' texi2html chokes on the source.

Upstream-Status: Inappropriate [disable feature]
Signed-off-by: Lawrence Velázquez <larryv@macports.org>

Index: doc/Makefile.in
===================================================================
--- doc/Makefile.in.orig
+++ doc/Makefile.in
@@ -649,10 +649,6 @@ uninstall-am: uninstall-dvi-am uninstall
 	uninstall-pdf-am uninstall-ps-am
 
 
-all-local: html
-install-data-local: install-html
-installdirs-local: installdirs-html
-uninstall-local: uninstall-html
 
 html: html-$(HTMLSTYLE)
 install-html: install-html-$(HTMLSTYLE)