Proposal: iOS should be a supported platform for Python development.

The attached patch is a first pass at a patch to achieve this. It is a single patch against Python 3.4.2 sources, and requires no pre- or post-configure modifications. 

Supporting iOS requires multiple builds - one for each of the hardware platforms that iOS supports (x86_64 simulator, ARMv7 and ARM64). These separate builds must then be merged into a single "fat" framework. The patch contains an iOS directory with a "meta" Makefile that manages this build-and-merge process. See the README in the iOS directory for details on usage.

The patch also introduces a new 'ios' platform type.

A sample XCode project for an iOS app is also provided as part of the patch.

iOS/README contains a couple of other notes about the build and the approach taken.

There are some known problems/limitations with this patch:

 * It's a patch against 3.4.2, not hg trunk

 * The code doesn't currently compile for ARMv7. In order to support ARM64, it has been necessary to use an unreleased trunk version of libffi; however, this version is currently broken for ARMv7. Older versions of libffi (including the formal 3.2.1 release) *do* work.

 * The patch doesn't currently provide any way to run the test suite on the target platform. Testing is currently based on a simple smoke test of some basic features.

So - the patch isn't ready for commit to trunk. I'm presenting it for the purposes of getting feedback on the broad approach while I continue to resolve the known issues.