WIP Changes for OSX

[aacuevas]

This is not meant to be merged, but as a WIP, to have it referenced on the main repository. For now centered around the ft600 driver.
There are only a few things to have into account for building the libaries for OSX, compared with:

• Some Makefile variables need to change depending of the architecture, namely -dynamiclib instead of -shared on LDFLAGS, as well the libraries extension.
• Small syntax changes to support clang
• Add the proper extension to onidriverloader.c

Also, there is a quirk related to how linking works on OSX. As binary linked against, for example, /usr/local/lib/libname.dylib will not work if the library is then relocated in any other path, even if the path is in the linker, as it stores the full path by default inside of it. There are ways around this, but is something to take into accout.