Represent 'unit' as C 'int'; change pattern match compilation to avoid 'goto'; change Postgres prepared statement compilation to make life easier for the GCC escape analysis; all this in support of better tail call optimization

table t : {A : int, B : int}
  PRIMARY KEY (A, B)

fun main () : transaction page =
    queryI (SELECT * FROM t) (fn _ => return ());
    return <xml/>