Remove Hugs98 specific code

For rationale, see
 http://permalink.gmane.org/gmane.comp.lang.haskell.ghc.devel/2349

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Constant-fold `__GLASGOW_HASKELL__` CPP conditionals

Now that HUGS and NHC specific code has been removed, this commit
"folds" the now redundant `#if((n)def)`s containing
`__GLASGOW_HASKELL__`.  This renders `base` officially GHC only.

This commit also inlines the `INSTANCE_TYPEABLE` macros and removes the
now superflous local `include/Typeable.h` header.

Finally, the `array.cabal` file is updated as well to remove the now
superflous conditionals.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>