droptofloor(): add/improve warnings for badly placed entities

droptofloor(): add/improve warnings for badly placed entities

In the past, sv_gameplayfix_droptofloorstartsolid and
sv_gameplayfix_droptofloorstartsolid_nudgetocorrect were enabled by
default when playing Quake, which seems to have led to some maps
depending on them.

These need to be off by default in Quake to avoid gameplay changes,
but we can at least warn people about map entity issues.

See: 34e819a626f6a7ff2ad190a8e7d42e38ca8cef0e

Signed-off-by: bones_was_here <bones_was_here@xonotic.au>