Fixes #1450.

See #1447.

Some people have old snapshots of 1.17 installed, which causes build failures.

platform, rather than assuming HOST == BUILD. This fixes things for cross compiling.

Comparison was using (>) instead of (>=). Bug introduced in 272a5c2c.
Fixes #1443.

This means that the package tests will pick up whatever GHC was passed
on the

    cabal configure --enable-tests -w some-ghc

command line.

Ignore 'ghc-options' when parsing 'ghc --info' output.

Pass linker options when loading *libraries* in GHCi.

Fixes #1438.

Fixes #1439. See also #1435, which fixed this for executables.

Conflicts:
	Cabal/Cabal.cabal

The flag `-outputdir` sets `-odir`, `-hidir`, `-stubdir`, and `-dumpdir`.

Using `-outputdir` has the benefit of redirecting all output files with
only one flag to a temporary directory.

Cabal currently only sets the first three but not the `-dumpdir` flag for
compiling Haskell modules, which clutters the top-level package directory
and sometimes dump files get overwritten if their names collide for
different build targets.

This minimal commit merely adds the `ghcOptOutputDir` flag to the data
structures and enables its use for the compilation of Haskell modules. A
later commit may remove the use of the now redundant `ghcOptStubDir` and
`ghcOptHiDir` flags in favor of the new `ghcOptOutputDir` flag.

The flag `-outputdir` is available since GHC 6.10; see also
ghc/ghc@bb074cb7 and
http://ghc.haskell.org/trac/ghc/ticket/2295

Calling ghci also needs the linker options

For a normal compile we do separate invocations of ghc for compiling as
for linking. But for repl we have to do just the one invocation, so
that one has to include all the linker stuff too, like -l flags and any
.o files from C files etc.

Need to see how .o files from C files works with ghci that uses dynamic
loading by default.

Improve stdout flushing

Fixes #1433.

Flushing after every line is helpful to see information quickly.

By default, Haskell application use NoBuffering when piped into
another process, which for example hides the output of cabal build
when run via a Continuous Integration server, an output-capturing
build tool, or ssh.

Build fix for Windows

Add sysconfdir.

Backwards compatibility patch for cross-compilation changes.

Describe new features in the documentation.