Added support for Frameworks on MacOS X.
*) On MacOS X, two additional command-line options are supported:
-framework <FRAMEWORK>    link with framework, gets passed on to ld
-framework-path <PATH>    gets passed on to ld as "-F<PATH>". (-F is already taken for GHC).
*) Two corresponding additional options for package.conf files:
framework_dirs
extra_frameworks
These options are allowed on any platform. They are ignored everywhere except on MacOS X.
*) ghc-pkg no longer uses Read. Instead, it uses a Happy parser. ghc/utils/ghc-pkg/ParsePkgConfLite.y is basically a copy of ghc/compiler/main/ParsePkgConf.y. "Light" refers to the fact that it doesn't depend on other GHC modules and has less sophisticated error reporting.
*) Frameworks will need some additional work for GHCi.