darcs patch: fix #1839, #1463, by supporting ghc-pkg bulkqueries with substring matching

[Claus Reinke]

> I agree with it: I think we want the functionality, we don't want to add
> a dep on a regex library, and using anything other than * for a wildcard
> would be confusing. I can't remember the details of the various Windows
> behaviours off the top of my head, so I can't comment on what the best
> solution would be.

sigh. i was afraid you might say that.

ok, i've hacked up a proof of concept that seems to 
behave as well as can be expected under these conditions,
switching off default globbing and using an extra program, 
glob (which just echoes its argument, after standard windows 
filename globbing), to get controlled globbing.

now, the question is: where do we want to allow filename 
globbing in ghc-pkg? the following involve files:

    register, update, FlagGlobalConfig, FlagConfig

but all of these seem to expect exactly one file, to be 
stored in a single FilePath? am i missing something,
or was this a wild goose chase?-)

> By the way, how did it work with regexps? Rely on no files matching .*,
> and the .* argument being left unchanged rather than being removed?

the regexp version had the same issues, but regexp patterns
gave a little more flexibility in avoiding accidental globbing.

claus