[opendemo-devel] character references added

[Conor D. <co...@ma...>]

I just comitted XML character reference support in od_xml_read.c, for
character data and attribute values. I tested it with a hand-edited demo
file (character data only) and it works.

I also made odr_write.c escape &, <, and > when writing configstrings and
server commands. I haven't tested this yet.

-Conor