add --ghc-args and such to configure

Done.

runhaskell Setup configure --with-ghc=... --ghc-args=...

These flags apply for all programs that cabal knows about (which is also extensible via hooks).

Done in the code, but not documented in the User's Guide.

A design issue: there is a difference in naming and semantics from --configure-option (and ghc-option elsewhere). The latter takes only one option, so multiple options must each be wrapped individually. That can be a bit more cumbersome, but it avoids issues with embedded spaces.

Now documented.

Also, I've added a --prog-arg= flag that behaves like --configure-option=.

I've also made --prog-args= parse it's args more cleverly. Instead of using words which breaks on files with embedded spaces we now use a slightly more clever lexer that allows simple quoting with "" chars. eg:

splitArgs "--foo=\"C:\Program Files\Bar\" --baz"
= ["--foo=C:\Program Files\Bar", "--baz"]

so on the command line you'd use:

./setup configure --foo-args='--bar="some path with spaces"'

That is the " chars have to be passed to setup, so if necessary they have to be escaped in the shell invocation.

The alternative of course is to use

./setup configure --foo-arg=--bar="some path with spaces"

again, assuming your shell parses --foo-arg=--bar="some path with spaces" into a single argument --foo-arg=--bar=some path with spaces.

Oh the joys of shell quoting.