Pick best python program available for 'make check'

Use an autoconf macro to find us a python executable, preferring python2.5
if we can find it. From there, fall back to python2.4 and then python.

Signed-off-by: Dan McGee <dan@archlinux.org>

Makefile.am

@@ -6,7 +6,7 @@ EXTRA_DIST = HACKING
 
 # run the pactest test suite
 check-local:  src/pacman
-	python $(top_srcdir)/pactest/pactest.py --debug=1 \
+	$(PYTHON) $(top_srcdir)/pactest/pactest.py --debug=1 \
 		--test $(top_srcdir)/pactest/tests/*.py \
 		-p $(top_builddir)/src/pacman/pacman
 	rm -rf $(top_builddir)/root

configure.ac

@@ -125,7 +125,8 @@ AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_PROG_MAKE_SET
 AC_PROG_RANLIB
-AM_PROG_LIBTOOL
+AC_PROG_LIBTOOL
+AC_CHECK_PROGS([PYTHON], [python2.5 python2.4 python], [false])
 
 # find installed gettext
 AM_GNU_GETTEXT([external])