Compiling clisp with Homebrew on Mac OS X Lion with XCode 4

LLVM in XCode 4 apparently doesn't define HAVE_STDBOOL_H. So, edit /usr/local/Library/Formula/clisp.rb and add the following line:

ENV['CFLAGS'] += ' -DHAVE_STDBOOL_H'

Put it somewhere after ENV.j1 in the install function.