Greenstack

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- Fixed PyGreenlet_SetParent signature, thanks to BoonsNaibot
- Fixed 64-bit Windows builds depending on wrong runtime dll

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- Better slp_switch performance on SPARC
- Drop support for Python 2.3
- Fix trashcan assertions on debug builds of Python
- Remove deprecated -fno-tree-dominator-opts compiler switch
- Enable switch code for SunStudio on 32-bit SunOS
- Support for abc abstract methods in greenlet subclasses
- Support custom directories for tests
- Document switch tracing support

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- Add .travis.yml
- Fix 'err' may be used uninitialized in this function
- Check _MSC_VER for msvc specific code
- Fix slp_switch on SPARC for multi-threaded environments
- Add support for m68k

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* fix segfaults when using gcc 4.8 on amd64/x86 unix
* try to disable certain gcc 4.8 optimizations that make greenlet
crash
* Fix greenlet on aarch64 with gcc 4.8
* workaround segfault on SunOS/sun4v
* Add support for Aarch64
* Add support for x32 psABI on x86_64
* Changed memory constraints for assembly macro for PPC Linux
platforms.

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* Greenlet has an instance dictionary now, which means it can be
used for implementing greenlet local storage, etc. However, this
might introduce incompatibility if subclasses have __dict__ in their
__slots__. Classes like that will fail, because greenlet already
has __dict__ out of the box.
* Greenlet no longer leaks memory after thread termination, as long as
terminated thread has no running greenlets left at the time.
* Add support for debian sparc and openbsd5-sparc64
* Add support for ppc64 linux
* Don't allow greenlets to be copied with copy.copy/deepcopy
* Fix arm32/thumb support
* Restore greenlet's parent after kill
* Add experimental greenlet tracing

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* Use plain distutils for install command, this fixes installation of
the greenlet.h header.
* Enhanced arm32 support
* Fix support for Linux/S390 zSeries
* Workaround compiler bug on RHEL 3 / CentOS 3