include the GHC package docs in a bindist

ghc.mk

@@ -919,6 +919,7 @@ $(eval $(call bindist,.,\
     $(INSTALL_LIBRARY_DOCS) \
     $(addsuffix /*,$(INSTALL_HTML_DOC_DIRS)) \
 	docs/index.html \
+	compiler/stage2/doc \
 	$(wildcard libraries/*/dist-install/doc/) \
     $(filter-out extra-gcc-opts,$(INSTALL_LIBS)) \
     $(filter-out %/project.mk mk/config.mk %/mk/install.mk,$(MAKEFILE_LIST)) \