ffi/ffi — pull request #300 by larskanis (2013-11-02 21:17:32+00:00)
Title: Fix test case so that it works on x86-mingw32 platform.

Currently the specs fail with one failure on x86-mingw32:
```
1) Custom type definitions detects the correct type for size_t
Failure/Error: lambda do
expected no Exception, got # with backtrace:
# ./lib/ffi/library.rb:261:in `attach_function'
# ./spec/ffi/typedef_spec.rb:74:in `block (4 levels) in '
# ./spec/ffi/typedef_spec.rb:70:in `initialize'
# ./spec/ffi/typedef_spec.rb:70:in `new'
# ./spec/ffi/typedef_spec.rb:70:in `block (3 levels) in '
# ./spec/ffi/typedef_spec.rb:69:in `block (2 levels) in '
# ./spec/ffi/typedef_spec.rb:69:in `block (2 levels) in '
```

The patch uses ```Platform.windows?```, which means MSVC++ and Mingw32 platforms (but not Cygwin). On these two platforms ```_read()``` can be used, instead.