remove last use of allocate

just use malloc instead
Merge pull request #310 from minrk/allocate

remove last use of allocate
Merge pull request #2 from minrk/pypy

Some PyPy fixes
add cffi stopwatch and remove skipped tests for

pypy
Merge Pull Request #307

PyPy Compatibility via CFFI backend
fix error checking in cffi backend

- `strerror` uses `ffi.string`
- use `_check_rc`
add install_requires for pypy
allowing cross-compilation from Linux to Android, also unused platform.hpp as a bonus
don't clean in the middle of a build
progress towards more sensible config

- [x] shouldn't suppress warnings where it won't work
- [x] manual overrides for a few things
- [x] allow skipping libzmq version check
- [x] cross compilation may or may not work
- [x] it shouldn't clean in the middle anymore, messing up bdists

Still some work to do.