Added a define EXTRAMACHDEPPATH which can be used to add sys.path items

for specific platforms. Use this to add plat-mac and
plat-mac/lib-scriptpackages on MacOSX. Also tested for not having adverse
effects on Linux, and I think this code isn't used on Windows anyway.

Fixes #661521.

configure

@@ -1,5 +1,5 @@
 #! /bin/sh
-# From configure.in Revision: 1.392 .
+# From configure.in Revision: 1.393 .
 # Guess values for system-dependent variables and create Makefiles.
 # Generated by GNU Autoconf 2.53 for python 2.3.
 #
@@ -1390,13 +1390,20 @@ echo "${ECHO_T}$MACHDEP" >&6
 
 # And add extra plat-mac for darwin
 
+
 echo "$as_me:$LINENO: checking EXTRAPLATDIR" >&5
 echo $ECHO_N "checking EXTRAPLATDIR... $ECHO_C" >&6
 if test -z "$EXTRAPLATDIR"
 then
 	case $MACHDEP in
-	darwin)	EXTRAPLATDIR="\$(PLATMACDIRS)";;
-	*) EXTRAPLATDIR="";;
+	darwin)
+		EXTRAPLATDIR="\$(PLATMACDIRS)"
+		EXTRAMACHDEPPATH="\$(PLATMACPATH)"
+		;;
+	*)
+		EXTRAPLATDIR=""
+		EXTRAMACHDEPPATH=""
+		;;
 	esac
 fi
 echo "$as_me:$LINENO: result: $EXTRAPLATDIR" >&5
@@ -17468,6 +17475,7 @@ s,@PYTHONFRAMEWORKINSTALLDIR@,$PYTHONFRAMEWORKINSTALLDIR,;t t
 s,@MACHDEP@,$MACHDEP,;t t
 s,@SGI_ABI@,$SGI_ABI,;t t
 s,@EXTRAPLATDIR@,$EXTRAPLATDIR,;t t
+s,@EXTRAMACHDEPPATH@,$EXTRAMACHDEPPATH,;t t
 s,@CXX@,$CXX,;t t
 s,@MAINOBJ@,$MAINOBJ,;t t
 s,@EXEEXT@,$EXEEXT,;t t