New opcode, STORE_MAP saves the compiler from awkward stack manipulations
and specializes for dicts using PyDict_SetItem instead of PyObject_SetItem.

Old disassembly:
              0 BUILD_MAP                0
              3 DUP_TOP
              4 LOAD_CONST               1 (1)
              7 ROT_TWO
              8 LOAD_CONST               2 ('x')
             11 STORE_SUBSCR
             12 DUP_TOP
             13 LOAD_CONST               3 (2)
             16 ROT_TWO
             17 LOAD_CONST               4 ('y')
             20 STORE_SUBSCR

New disassembly:
              0 BUILD_MAP                0
              3 LOAD_CONST               1 (1)
              6 LOAD_CONST               2 ('x')
              9 STORE_MAP
             10 LOAD_CONST               3 (2)
             13 LOAD_CONST               4 ('y')
             16 STORE_MAP

Amaury's ideas works great. Should we build the Python core with WINVER=0x0500 and _WIN32_WINNT=0x0500, too?

is now simpler.  Thanks Mark Dickinson.

I had to modify Brett's patch slightly.

pointer copy and object increment in one pass.  For small lists,
save the overhead of the call to memcpy() -- this comes up in
calls like f(*listcomp).

The detection now works on Unix with Makefile, Makefile with VPATH and on Windows.

Thanks to Ian Bruntlett and Robert Lehmann.

I added also the feature that a @prop.getter decorator does not overwrite the doc string of the property if it was given as an argument to property().

run it and check in the resulting configure file.