Can people please test ffi-master on your favourite ruby version?

Things fixed since 1.0.9:

- should now work on 1.9.3 (ruby_thread_has_gvl_p no longer exported)
- installs on non-MRI rubies
- compiles using VC++ toolchain on win32 (Charlie Savage)
- a lot of API documentation (Kim Burgestrand)
- other win32/win64 mingw fixes (Luis Lavena)
- better handling of linker scripts on linux (aniederl)
- ext/ffi_c/StructLayout.c fixes (Chikanaga Tomoyuki)
- Size lookup for MemoryPointer.new and Buffer.new type
(e.g. :int, :long, etc) parameters now much faster.
- FFI::Buffer.new for small sizes (<= 8 bytes) types now approx 30%
faster.

I especially would like people to test on 1.9.3-preview1 (or later
1.9.3 builds/source), since I want the release to work out-of-the-box
on 1.9.3.