Merge ast-branch to head

This change implements a new bytecode compiler, based on a
transformation of the parse tree to an abstract syntax defined in
Parser/Python.asdl.

The compiler implementation is not complete, but it is in stable
enough shape to run the entire test suite excepting two disabled
tests.
diff --git a/Parser/grammar.mak b/Parser/grammar.mak
index a6f1abe..55f028f 100644
--- a/Parser/grammar.mak
+++ b/Parser/grammar.mak
@@ -15,7 +15,7 @@
 # particular case --pragma in PC\pyconfig.h, which demands that
 # python23.lib get linked in).
 
-LIBS= ..\PCbuild\python23.lib
+LIBS= ..\PCbuild\python25.lib
 
 CFLAGS= /I ..\Include /I ..\PC /D MS_NO_COREDLL /D PGEN /MD