mod_lua: Error out if lua_read_body() or lua_write_body() fail.

Otherwise r:requestbody() or r:parsebody() failures might go unnoticed for
the user.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1898689 13f79535-47bb-0310-9956-ffa450edef68
