The original error from the OP was due to issues in changes in the kernel around 2.6.26. This is an old driver and came out before the kernel was finished. It is advised to use the svn version instead, as that should compile against current kernels.
But if you really want to compile the 0.9.4 version it is best to just download it from madwifi-project.org subversion directory, which contains all of the latest patches.
It compiled fine with gcc-4.2. It also compiled fine for me with gcc-4.3, although there were a couple of warning messages near the end of make command.
# svn co http://svn.madwifi-project.org/madwifi/branches/madwifi-0.9.4/ madwifi-ng-0.9.4
# cd madwifi-ng-0.9.4
# apt-get install gcc-4.2
# make CC=gcc-4.2