Add 'make list_brokens'

Gives a list of tickets that the testsuite thinks are broken, and
what bug it thinks is the reason. This can then be pasted into trac
and 'previewed', which will show any closed tickets with strikeout.
Replace 'if_os' and 'unless_os' with 'opsys'

The name 'os' clashes with a python library
expect_broken_for should also be added to the list of brokens
Handle duplicates in the brokens list
Print a warning if we get framework failures when listing brokens
Change '{if,unless}_arch' to 'arch'
Convert more helpers to the new scheme
Convert more helper functions to the new scheme
Convert more helper functions
Convert more helpers
More helper conversions
More conversions
Merge branch 'master' of darcs.haskell.org:/srv/darcs//testsuite