Fix OSX build

[emillon]

At the moment the build fails on osx.

Make it possible to either:

• not build the reverse bindings (the only part that fails)
• build the reverse bindings on osx.

The current solution (disable the whole package on osx) also works. To anyone interested: patches welcome :)

[vbgl]

The dlfcn.h header is available on osx. It seems enough (at least, it fixes the build) to generalize the #if defined(__linux__) || (defined(__sun) && defined(__SVR4)) conditional to include defined(__APPLE__).

[emillon]

Hi,

Great, I don't have an OSX system so I did not know what was the macro to use.

If you submit a pull request making sure that it builds and the tests pass, I'll include that in the next release.

Thanks!

[yallop]

It could be useful to add an OS X entry to the Travis configuration to ensure that the build keeps working.

[emillon]

@yallop IIRC OSX support for Travis makes really long builds, I don't think it's worth having it permanently enabled.