GHC 6 for Mac OS X: fix for package util/readline

On Mac OS X GHCi 6.0 complains about a missing symbol when trying to 
load package "util". Wolgang Thaller told me the cause of this bug:

The problem was that there was a file called HsReadline.c. The 
corresponding
object file, HsReadline.o, replaced HSreadline.o on the Mac's
case-insensitive file system.

So the actual problem is a broken readline package, which is used by 
util.
The bug is fixed in the next release (6.0.1) and in CVS. For those who 
don't feel like compiling CVS-sources, or waiting for the next release; 
below is a quick fix. A working HSreadline.o is created from the 
libHSreadline.a file using the -g option of ghc-pkg.

1) set environment variable "libdir" to ghc-6's directory:
    setenv libdir /usr/local/lib/ghc-6.0/
2) cp $libdir/libHSreadline.a $libdir/libHSreadline_p.a /tmp/
3) create a config file for package readline:
    ghc-pkg -s readline > /tmp/readline.conf
4) cd /tmp
5) remove the package readline from ghc:
    ghc-pkg -r readline
6) add package again and let ghc-pkg create the ghci library:
    ghc-pkg -g -a -i /tmp/readline.conf

For step 5/6 you may need root-access, use "su" or "sudo"

Arthur