implement make-style module/file dependency framework

[ijones]

Implement inter-module dependency analysis. This will improve a number of features, including:

• Obviate other-modules field
• Building DLLs?

We might be able to use the code from HMake, but must check w/ copyright holders.

[duncan]

See also:

• ticket #159
•  proptotype of make style dep stuff

[duncan]

Upping priority. So many other bugs and features depend on this.

[duncan]

Other tickets that need a dependency framework:

#13 #16 #17 #34 #48 #89 #104 #110 #128 #131 #159 #171 #188

[guest]

See also:

• #216 - specify more kinds of dependencies in .cabal files
• #177 - check for required directories
• # 262 - check for required foreign libraries

[guest]

#262 - check for required foreign libraries

[duncan]

We're getting confused about dependencies here. This ticket is about dependencies between modules and files within a single package, not dependencies between packages or dependencies of packages on foreign libs.

So #216 #177 and #262 are not relevant to this ticket.

[duncan]

Changing the ticket title to try and reduce confusion over what kind of dependencies we're talking about.

[EricKow]

As a potential user of this feature, we in the darcs world are mostly interested in this because we want to do parallel builds (like make -j)