naemon/xrddefault.c: removing references to Nagios(tm)

removed some old references to Nagios(tm) from retention file.

Signed-off-by: Ricardo Maraschini <ricardo.maraschini@gmail.com>
Merge pull request #48 from ricardomaraschini/retention-strings

naemon/xrddefault.c: removing references to Nagios(tm)
Don't use const char const *method(), only const char *method()

The data the method is pointing to is constant, so the first const is
valid. And the pointer those methods return will be the same each time,
so the second const makes sense. But the second const only means that
the method is deterministic, which isn't the same as const.

The second const (which is placed after the method actually) in C++
means it won't affect the objects internal values. But that doesn't
make sense in C.

Signed-off-by: Max Sikstrom <msikstrom@op5.com>