"install-data-hook" compresses manual pages.  Stop doing that.

Index: doc/Makefile.in
--- doc/Makefile.in.orig
+++ doc/Makefile.in
@@ -663,7 +663,7 @@ info-am:
 install-data-am: install-gnubg_helpDATA install-gnubg_imageDATA \
 	install-man
 	@$(NORMAL_INSTALL)
-	$(MAKE) $(AM_MAKEFLAGS) install-data-hook
+	$(MAKE) $(AM_MAKEFLAGS)
 install-dvi: install-dvi-am
 
 install-dvi-am:
