patch applied (cabal): Generalise PreProcessors to take more detailed args

[Duncan Coutts]

Sun Apr 22 03:05:58 PDT 2007  Duncan Coutts <duncan.coutts at worc.ox.ac.uk>
  * Generalise PreProcessors to take more detailed args
  Most pre-processors just need the full source file and target file names.
  More complicated ones where the generated files have to embed links to each
  other need more information. For example c2hs generates .hs file that
  reference generated .h files. These links should be relative to the dist/build
  dir and not to the top of the source tree, since we do not want to add -I. to
  the includes search path. We only want to use -Idist/build, hence the embeded
  links must be relative to that. Therefor c2hs needs to know the base output
  directory as well as the name of the file relative to that.
  So we add a new type PreProcessorFull that has this extra info and a function
  simplePP :: :: PreProcessor -> PreProcessorFull
  for the common case of most existing pre-processors that do not need this
  extra info.
  This patch doesn't actually change the c2hs stuff, that comes next.

    M ./Distribution/PreProcess.hs -11 +47