[project @ 2002-04-10 09:41:16 by simonmar]

Currently configure falls over if $srcdir/ghc exists and Happy >= 1.9
can't be found.  For a source distribution this is too paranoid,
because we ship the Happy-generated .hs files with the sources.  Now
we ignore a missing Happy if ghc/compiler/parser/Parser.hs exists,
which should be a reasonable heuristic.