package descriptions

[ross at soi.city.ac.uk]

I'd like to propose a refactoring of the package description, as follows:

(1) The unprocessed source tree of every package would contain a package
    description, consisting a single stanza:

	name:		unique name of the package (compulsory)
	version:	package version number (compulsory)
	license:	identifier for a common license (compulsory)
	license-file:	name of a file containing the license
	copyright:	copyright holder (compulsory)
	author:		original author of the package
	maintainer:	current maintainer of the package (if different)
	stability:	stability level
	homepage:	URL of the package homepage
	package-url:	(same as homepage?)
	description:	free-text description of the package
	category:	from a list to be specified
	tested-with:	list of compilers and versions (?)
	build-depends:	list of packages needed to build this one
	exposed-modules: list of modules added by this package
	executables:	list of programs added by this package

(2) Packages using the simple build infrastructure would optionally
    provide an additional file of build parameters for that infrastructure,
    consisting of a basic stanza and zero or more executable stanzas:

	build-package:	Boolean: is package buildable? (default: True)
	<buildinfo>	(for library, if any)

	executable:	name of a program from executables
	main-is:	relative filename for the main module
	<buildinfo>	(for the executable)

    where <buildinfo> consists of:

	other-modules:	list of additional modules
	hs-source-dir:	name of root directory of the module hierarchy
	extensions:	list of Haskell extensions used by every module
	options-ghc:	additional options for GHC
	options-hugs:	additional options for Hugs
	options-nhc:	additional options for NHC
	c-sources:	list of C source files
	cc-options:	options for the C compiler
	includes:	header files describing foreign imports
	include-dirs:	directories to search for header files
	ld-options:	options for the linker
	extra-libs:	extra libraries to link with
	extra-lib-dirs:	directories to search for libraries
	frameworks:	list of Darwin/MacOS X frameworks to link to

    (The options fields are inconsistent -- we can sort that out later.)

    This file need not be present until after the pre-conf step; in some
    cases it will be generated from a template by that step.