devel: 'eval' returns 0 upon syntax error

[Martijn Dekker]

bash-snap-20170616

$ (eval '(');echo $?
bash: eval: line 2: syntax error: unexpected end of file
0

The exit status is 0, but should be 1.

As far as I can trace it, this bug seems to have been introduced in
bash-20170511 snapshot.

- M.