Rework how iOS does linking (#8127)

iOS has some particular constraints about how applications can be built:

 * We must generate a static library (.a) since XCode does the final
   link.
 * We need to carefully give the right set of arguments to libtool in
   the case we're generating an archive.
 * Dynamic linking isn't supported.
 * It can only be done on OS X.

This patch cleans up all of the above. We add a new flag `-staticlib`
(only supported on Darwin) that allows us to produce archive files using
libtool, and a -pgmlibtool flag to control which 'libtool' executable to
use.

This fixes #8127. I believe this is the last piece missing from the iOS
cross compiler.

Authored-by: Luke Iannini <lukexi@me.com>
Authored-by: Maxwell Swadling <maxwellswadling@gmail.com>
Authored-by: Stephen Blackheath <...@blacksapphire.com>
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Applicative instance for Ghc and GhcT

Fixes #8175.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Implement -XNumDecimals (#7266)

Under -XNumDecimals, it's possible to specify an integer literal using
compact "floating point" syntax for any floating literal constant which
also happens to be an integer. This lets us write

    1.2e6 :: Integer

instead of:

    1200000 :: Integer

This also makes some amendments to the users guide.

Authored-by: Shachaf Ben-Kiki <shachaf@gmail.com>
Signed-off-by: Austin Seipp <aseipp@pobox.com>
Detabify RnPat.lhs

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Document -XNegativeLiterals in the relase notes.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Wibbles.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Mention iOS cross compilation in release notes.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Wibbles.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
Fix validate failure.

Signed-off-by: Austin Seipp <aseipp@pobox.com>
More docs for -XNumDecimals

Signed-off-by: Austin Seipp <aseipp@pobox.com>