add flag to dump module and package dependencies

You can already dump module and package dependencies with -M -include-pkg-deps, but it wants to modify a Makefile, so it's not so convenient for things that are not make. For other build systems, it would be convenient to get this on stdout in an easily parseable form. Say X/A.hs imports Y/B.hs, which imports Z/C.hs, and they all use package 'base' and 'containers':

% ghc -Mstdout X/A.hs
X/A.h
Y/B.hs
Y/B.hs
Z/C.hs

base containers
%

I don't know about what the output format should be, but assuming no newlines in filenames, and package names never have spaces, it seems simplest to do something like:

[src ++ "\n" ++ dest ++ "\n" | (src, dest) <- moduleDeps] ++ "\n" ++ unwords packageDeps

It could use haskell syntax like --info, but then you'd need a full haskell parser just to read it, which is not a problem for shake, but probably inconvenient for other build systems.

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Trac field	Value
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Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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