src/help.c interactive_display () removing unused argument

[vit_r]

src/help.h
void interactive_display (const char *filename, const char *node);

All calls start with 'NULL' as first argument like this:

interactive_display (NULL, ...);

May be it was used but now seems there is no more need

[vit_r]

2097-src-help.c-interactive_display-rm-UNused-argument.patch

is attached to ticket #2097