pygrub's setup.py relies on distutils.UnixCCompiler.has_function(),

pygrub's setup.py relies on distutils.UnixCCompiler.has_function(),
which does not exist with python2.2, causing the following build
error:

make[2]: Entering directory `/home/muli/xen/x86.hg/tools/pygrub'
CFLAGS=" -m32 -march=i686" python setup.py build
Traceback (most recent call last):
  File "setup.py", line 15, in ?
    if cc.has_function("ext2fs_open2"):
AttributeError: UnixCCompiler instance has no attribute 'has_function'

The following patch gets it to build, but is pretty ugly. A proper fix
would be to do the check for ext2fs_open2() in a way that is backward
compatible with python2.2.

Signed-Off-By: Muli Ben-Yehuda <mulix@mulix.org>