Fix compilation of Swift bindings

[meshula]

Fixes #736

Summarize your change.

• fixes conflicts with objc.h macro bool by using BOOL_ instead of BOOL. Arguably BOOLEAN is preferable to BOOL, but I'd prefer to address that in a separate PR.
• changes signing identity to "-" and team to none.
• Now looks for libopentime.dylib and libopentimelineio.dylib in /usr/local/lib. There should be a better way to handle this, but that is a fairly normal place to look for user dylibs.
• fixes a use of the to_string API which has changed

Reference associated tests.

The Swift bindings already have a great set of tests. Not all of them currently pass. In order to test yourself, libopentime.dylib and libopentimelineio.dylib must be place manually in the derived data folder. In my case, the necessary command was:

cp /usr/local/lib/*.dylib ~/Library/Developer/Xcode/DerivedData/otio-swift-akeblvbkhzdlqhdofukkdrtirvum/Build/Products/Debug

If anyone knows the right way to get the dylibs into the test, please LMK.

Currently the opentime bindings pass three quarters of the tests. opentinelineio fails immediately in a clone operation, and so none of the tests run.

[davidbaraff]

Looks good to me.

[reinecke]

Great start to getting Swift bindings back in the mix!

[jchen9]

There's this old WIP pull request: #508

It has an OTIO-Swift.framework target, which would build & embed dylibs inside the framework. With it, you could set test target depending on and linking to it.

It was based on the old cxx branch but there might still have something useful... :)

[meshula]

@jchen9 Ah, cool! A PR yet to be submitted moves the Swift bindings into its own repo. The new repo would be a great opportunity to introduce the Swift demo app and other goodies you included with #508!