Gideon : Minor fix to NonterminalMatcherfactory which should use
joshuaConfiguration.default_non_terminal to get the identity of the
default-nonterminal / OOV symbol, rather than a hard-coded [OOV] String.
The default-nonterminal is used in unary or glue rules to be able to produce
unknown words, but to avoid spurious ambiguity or weird unary chains
when performing soft syntactic decoding, it should not be allowed to
match or be matched to anything but itself, just like for the goal symbol.

	modified:   src/joshua/decoder/chart_parser/NonterminalMatcherFactory.java