Revert "support generation of manual in ePUB format"

SOURCES=$(wildcard src/*.txt)

OBJECTS=$(SOURCES:src/%.txt=$(RSTDIR)/%.rst)

.PHONY: help clean-all clean epub html pdf old venv

.PHONY: help clean-all clean html pdf old venv

# ------------------------------------------

	@echo "  pdf        create Manual.pdf and Developer.pdf in this dir"

	@echo "  old        create old-style HTML doc pages in old dir"

	@echo "  fetch      fetch HTML and PDF files from LAMMPS web site"

	@echo "  epub       create ePUB file with manual in this dir"

	@echo "  clean      remove all intermediate RST files"

	@echo "  clean-all  reset the entire build environment"

	@echo "  txt2html   build txt2html tool"

	@rm -rf html/USER/*/*.[sg]*

	@echo "Build finished. The HTML pages are in doc/html."

epub: $(OBJECTS)

	@(\

		. $(VENV)/bin/activate ;\

		cp -r src/* $(RSTDIR)/ ;\

		sphinx-build -j 8 -b epub -c utils/sphinx-config -d $(BUILDDIR)/doctrees $(RSTDIR) epub ;\

		deactivate ;\

	)

	@mv -f epub/LAMMPS.epub .

	@rm -rf epub

	@echo "Build finished. The ePUB file LAMMPS.epub is created/updated."

pdf: utils/txt2html/txt2html.exe

	@(\

		cd src; \