Prior to this change, if you tab-completed a token with a wildcard (glob), we
would invoke ordinary completions. Instead, expand the wildcard, replacing
the wildcard with the result of expansions. If the wildcard fails to expand,
flash the command line to signal an error and do not modify it.
Example:
> touch file(seq 4)
> echo file*<tab>
becomes:
> echo file1 file2 file3 file4
whereas before the tab would have just added a space.
Some things to note:
1. If the expansion would produce more than 256 items, we flash the command
line and do nothing, since it would make the commandline overfull.
2. The wildcard token can be brought back through Undo (ctrl-Z).
3. This only kicks in if the wildcard is in the "path component
containing the cursor." If the wildcard is in a previous component,
we continue using completions as normal.
Fixes#954.
