bug#17284: Host name completion in shell mode take 45 seconds

[martin rudalics]

> `buffer-substring-no-properties' is defined in C.  I can't tell
> whether this is more efficient because of that or less efficient
> because it creates a potentially giant string before starting to
> compare.  I was trying to compare starting from the far end,
> thinking that that might lead to earlier failure detection.

I got your idea.  But you also said that what we are handling here is
"typically a short string" ;-)

martin