invalid nasty_metachars example

[peekjef72]

by default, the configuration file reader checks for varname=varvalue; so adding doublequotes at the begin of the text causes this character to be considered as a nasty char, and that is not the default behavior (the internal default string).

[sawolf]

Yep, looks like this was copied from the #define NASTY_METACHARS line in nrpe.c. Good catch.