Define error/1 in terms of error/0

The parser generates a call to error/0 on break. Having that exported
from C directly removes a language dependency on builtin.jq.

In any case, error/0 seems to be the more fundamental operation, seeing
as the old C impementation of error/1 did nothing useful with its input.

src/builtin.jq

@@ -1,5 +1,5 @@
 def halt_error: halt_error(5);
-def error: error(.);
+def error(msg): msg|error;
 def map(f): [.[] | f];
 def select(f): if f then . else empty end;
 def sort_by(f): _sort_by_impl(map([f]));