Fix Content-Range generation bug
(cherry picked from commit 9f444a680e4f15cd670b94591406ddd3f2fbcf0b)
Fix return value of process_request and related subroutines

1) Only HTTP_XXX should be return
2) Make default return value work for process_request
(cherry picked from commit 06aa3b17c4e20c482de3865b4e8608077db8284b)

Conflicts:
	upnp/src/genlib/net/http/webserver.c
Fix return value of http_RecvPostMessage and update httpparser.c's comments
(cherry picked from commit 062ac0c92621e1ace5e7400c8d3509327fd5c4ce)