Library is broken on Mac OSX

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When using the library on Mac OSX, most things will fail because the library 
tries to PInvoke to libdl.so, which does not exist on OSX.  On OSX, dload() and 
friends are provided by libSystem.B.dylib.

I've attached a patch that adds the necessary logic.

I've also attached some changes that make the build system and unit tests pass 
on OSX.  The primary changes are using Path.Combine to concatenate path 
fragments rather than assuming any particular character, and the introduction 
of a silly little bash-batch polyglot application to ensure that 
AssimpNet.Interop.Generator.exe is invoked via mono.

Original issue reported on code.google.com by andy.fri...@gmail.com on 30 Aug 2014 at 8:54

Attachments:

• 0001-Add-OSX-support-dload-and-friends-are-found-in-a-dif.patch
• 0002-Make-unit-tests-run-on-OSX-Rely-on-Path.Combine-to-k.patch
• 0003-Tweak-post-build-action-to-work-on-OSX-CLR-executabl.patch