parser: separate actions for primary expression and prefix operator...
parser: separate actions for primary expression and prefix operator
This will allow us to define both a primary expression, ":", and a prefix
operator, ":y". The ambiguity will be resolved by the next patch.
Prefix actions in elements table are adjusted as follows:
original prefix primary prefix
----------------- -------- -----------------
("group", 1, ")") -> n/a ("group", 1, ")")
("negate", 19) -> n/a ("negate", 19)
("symbol",) -> "symbol" n/a
