lots of portability changes (#1405)

re-recording to avoid new conflicts was too hard, so I just put it
all in one big patch :-(  (besides, some of the changes depended on
each other.)  Here are what the component patches were:

Fri Dec 28 11:02:55 EST 2007  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * document BreakArray better

Fri Dec 28 11:39:22 EST 2007  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * properly ifdef BreakArray for GHCI

Fri Jan  4 13:50:41 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * change ifs on __GLASGOW_HASKELL__ to account for... (#1405)
  for it not being defined. I assume it being undefined implies
  a compiler with relatively modern libraries but without most
  unportable glasgow extensions.

Fri Jan  4 14:21:21 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * MyEither-->EitherString to allow Haskell98 instance

Fri Jan  4 16:13:29 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * re-portabilize Pretty, and corresponding changes

Fri Jan  4 17:19:55 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * Augment FastTypes to be much more complete

Fri Jan  4 20:14:19 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * use FastFunctions, cleanup FastString slightly

Fri Jan  4 21:00:22 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * Massive de-"#", mostly Int# --> FastInt (#1405)

Fri Jan  4 21:02:49 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * miscellaneous unnecessary-extension-removal

Sat Jan  5 19:30:13 EST 2008  Isaac Dupree <id@isaac.cedarswampstudios.org>
  * add FastFunctions