modify py threading demo
add xcb hello, both c and py
Merge branch 'master' of https://github.com/jzou2000/codex

merged from github:
improved
	epub.py			convert downloaded htmls into epub
	epub2html.py		convert epub into htmls/frames
	gui/xpy.py		minor
	distill/lang.txt	add boost::format, py format
added
	json4epub.txt		description of json files used by epub.py
	distill/xcb.txt		common objects in xcb and app pattern
	gui/gtkmm-hello.cpp	sample of gtkmm
	gui/xcb/xt.py		simple simulation of xt from xcb
	threading/dining.c	threading samples - typical
	threading/pc.c		threading samples - typical
	threading/rw.c		threading samples - typical
deleted
	bin/index2frame.py	replaced by epub2html.py
	bin/epub2index.py	replaced by epub2html.py