This is one of two commits aimed at reducing the gap between Hugs-supplied libraries and their GHC counterparts.  The ultimate goal is to make the fptools/hslibs libraries work with Hugs.
This is one of two commits aimed at reducing the gap between
Hugs-supplied libraries and their GHC counterparts.  The ultimate goal
is to make the fptools/hslibs libraries work with Hugs.

Progress towards this goal: all hslib libraries work (== are loaded
without error by Hugs) except those which use casm/ccall (net and
posix) and the ffi-related hslib/lang libraries which are usually
wafer-thin layers over the ghc Prelude code.  (Commits to hslib have
not yet been done - waiting for the hslib folk to give me the nod.)

This particular commit brings Hugs into line with the very recent (and
very welcome) changes to the Exception API and includes dummy (nullop)
implementations of block and unblock whose use pervades the hslib
libraries.

FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs,FranklinChen/Hugs