As a first step in unifying test_decimal.py and test_cdecimal.py I
would like to patch test_decimal.py in trunk and py3k. This is to
minimize differences between py3k and py3k-cdecimal.

(1) Remove test that Decimal(x) generates a copy.

(2) Add test case to formatting test.

(3) Extend threading test.

(4) Use Emax of 425000000 instead of 999999999 where possible.
    (The 32-bit version of cdecimal has the official limit of
    425000000, even though 999999999 works in almost all cases.)


If I get an OK for the two patches, I can commit them to py3k and
trunk. If you don't want to apply (1), I'll make new patches.