darcs patch: add extra-includes field to buildinfo

Hi, please consider the attached patch. It allows installing include files into $(lib)/include without automatically including them in compilations via C. Use cases can be found in the package description below. The base package could take advantage of this feature immediately. The patch is possibly incomplete: the field is completely ignored when installing packages for Hugs, which is bad if the header files are indeed used for Haskell code in a different package. Bertram Thu Apr 19 12:42:24 CEST 2007 Bertram Felgenhauer * add extra-includes field to buildinfo The patch targets packages that come with an include file which includes other include files in turn, or packages that want to install header files that are used for preprocessing Haskell code rather than C code. This will allow the base package to install its header files properly.