Parses a single definition list entry of the form : key : value.
The function expects startPos to point at a line-start COLON token.
It consumes the first colon, mandatory whitespace, key tokens up to
the second colon, then value tokens until a double newline, a new entry,
or end of input.
Parses a single definition list entry of the form
: key : value.The function expects
startPosto point at a line-start COLON token. It consumes the first colon, mandatory whitespace, key tokens up to the second colon, then value tokens until a double newline, a new entry, or end of input.