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	Improve the dynamic-linking story
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Arrange proper initialisation for the dynamic linker.  Whenever the dynamic linker does
anything (Linker.linkExpr), it first initialises itself, arranging to only do so once
of course.

"Initialising itself" includes loading any .o files, libraries, and packages specified
on the command line.  The main effect of all this is to fix a Template Haskell problem,
which happened when a TH link needed some C library that it couldn't link.  Now it does.



While I was at it, I tidied up main/Main.hs quite a bit.  This is a delicate area (handling
the command line arguments), but I don't believe I broke anything!  All the libraries
build, and lots of tests run.

Wolfgang: I also jiggled the darwin_TARGET_OS stuff a little in Linker.lhs, but again
I think the net effect is zero. You might want to check.