Improved __future__ parser; still more to do

Makefile.pre.in: add target future.o

Include/compile.h: define PyFutureFeaters and PyNode_Future()
                   add c_future slot to struct compiling

Include/symtable.h: add st_future slot to struct symtable

Python/future.c: implementation of PyNode_Future()

Python/compile.c: use PyNode_Future() for nested_scopes support

Python/symtable.c: include compile.h to pick up PyFutureFeatures decl
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 43a7f79..94aa576 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -200,6 +200,7 @@
 		Python/errors.o \
 		Python/frozen.o \
 		Python/frozenmain.o \
+		Python/future.o \
 		Python/getargs.o \
 		Python/getcompiler.o \
 		Python/getcopyright.o \