If your C# runtime environment supports unsafe mode, you can use
the #define UNSAFE_BYTEBUFFER setting and build the FlatBuffers assembly
in unsafe mode for greatly increased performance.

Tested: Tested FlatBuffersTest on Windows using VS2010 with both safe
and unsafe versions. Added ByteBufferTest to test the byte reversing
functions.

Change-Id: I21334468b339334f9abf4317e6291b648b97f57b