Partial fix for #887242 (link extensions with dynamic_lookup in stead
of hard linking against the framework).

If $MACOSX_DEPLOYMENT_TARGET is set, and >= 10.3, during configure we
setup extensions to link with dynamic lookup. We also record the
value in the Makefile.

Distutils checks whether a value for MACOSX_DEPLOYMENT_TARGET was
recorded in the Makefile, and if it was insists that the current
value matches.

This is only a partial fix because it only applies to 2.4, and the
"two python problem" exists with Python 2.3 shipped with MacOSX 10.3,
which we have no influence over.
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 074fba4..e4a12b0 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -107,6 +107,9 @@
 PYTHONFRAMEWORKDIR=	@PYTHONFRAMEWORKDIR@
 PYTHONFRAMEWORKPREFIX=	@PYTHONFRAMEWORKPREFIX@
 PYTHONFRAMEWORKINSTALLDIR= @PYTHONFRAMEWORKINSTALLDIR@
+# Deployment target selected during configure, to be checked
+# by distutils
+CONFIGURE_MACOSX_DEPLOYMENT_TARGET=@CONFIGURE_MACOSX_DEPLOYMENT_TARGET@
 # Options to enable prebinding (for fast startup)
 OTHER_LIBTOOL_OPT = -prebind -seg1addr 0x10000000