shell_eof_token not reset after interrupt

[Grisha Levit]

If SIGINT is received while parsing a command substitution, the top-
level parser ends up with an incorrect shell_eof_token.

This results in incorrect messages for subsequent syntax errors:

    $ $(
    > ^C
    $ ;
    bash: syntax error near unexpected token `;' while looking for matching `)'

And a non-working verbose mode:

    $ set -v
    $ : xxxx
    $