Make all classes new-style.

[jamadden]

On PyPy, it's documented (http://pypy.org/performance.html#id3) that old-style classes are slow, and classes that derive from both old and new are especially slow. I checked with the PyPy devs on IRC today and they confirmed that's still true with the latest PyPy2 releases.

Unfortunately, FileStorage was one such mixed class (due to UndoLogCompatible), as was Connection (due to ExportImport).

Moving to new-style classes seems to have a positive impact in the benchmarks. Here's zodbshootout on PyPy2 5.7.1 against a FileStorage (running in --threads and with 5 reps to be sure we get warmed up). First, current ZODB:

"Transaction",                fs
"Add 1000 Objects",            31,738
"Update 1000 Objects",         42,444
"Read 1000 Cold Objects",      51,894
"Read 1000 Hot Objects",       53,187
"Read 1000 Steamin' Objects", 835,877

And with this PR:

"Transaction",                fs
"Add 1000 Objects",             35,651
"Update 1000 Objects",          54,906
"Read 1000 Cold Objects",      103,484
"Read 1000 Hot Objects",        84,721
"Read 1000 Steamin' Objects", 2,112,095

The tests that hit the storage extensively are notably faster, as are steamin and hot (Connection having been a mixed class).

I ran all tests multiple times. The data files were removed between runs. There's some variation, but the new-style classes always seem better.

For comparison, here's CPython 2.7.13:

"Transaction",                fs
"Add 1000 Objects",            19,531
"Update 1000 Objects",         16,201
"Read 1000 Cold Objects",      22,111
"Read 1000 Hot Objects",       21,851
"Read 1000 Steamin' Objects", 880,582

Locally I've run the tests under 2.7 and they all passed.

Besides the benchmark improvements, this makes Python 2 closer to Python 3 for those classes.

This was a mechanical transform (with only one mis-change reverted) produced by this script:

$ sed -E -i "" "s/class ([[:alnum:]_]*):/class \1(object):/g" `find src -name "*.py"`

[jmuchemb]

can you recheck with s/^(\s*)class ([[:alnum:]_]*):/\1class \2(object):/g ?

[jamadden]

Thanks for finding that!

Unfortunately the other regex misses not just the things that are in docstrings/doctests (which aren't important for performance, granted, but are important for consistency) but it also missed a handful of classes (E.g this one) for some reason.

[jamadden]

Rebased on master to resolve CHANGES.rst conflict with #161.

[jimfulton]

Thanks.