log_flags.cpp

    (it wasn't setting the "use_XXX" flags).  Fixes #776
- client: you can now include a <proxy_info> element
    in your cc_config.xml options.

TODO: the whole proxy info thing needs an overhaul:
- no separate "use_XXX" flags;
    non-empty http_server_name implies using HTTP proxy, etc.
- merge PROXY_INFO and GR_PROXY_INFO classes
- use XML_PARSER for parsing
- no PROXY_INFO element in HTTP_OP; just use gstate.proxy_info

svn path=/trunk/boinc/; revision=17379