A 4GL function may return different things on different paths - a value on one
and nothing on another, or a SMALLINT here and a DECIMAL there. fglproto emits
one prototype per shape, and is_bolton_function answered with whichever came
first, so which shape a back end saw depended on the order they happened to be
written. Arbitrary, and for a back end with a strict type system it decides
whether the program compiles at all.
The widest now wins: a function returning SMALLINT on one path and DECIMAL on
another is a DECIMAL function, and the narrow value converts to it without
loss. Where two shapes return different numbers of values the one returning
more wins, so no call site loses a result.
Ordering is SMALLINT < INTEGER < INT8 < DECIMAL < FLOAT < CHAR, comparing at
the first position where two shapes differ.
No change to the C back end's output on the example suite - it accepts either
shape, so it never depended on the choice.
