FFI error handling

[ghost]

Purpose

Returns result with possible error codes from FFI calls.

Changes

• Added better error handling from FFI by returning error code indicating the type of error
• Make exception with error code public such that it can be caught by clients

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.

[ghost]

Hi @limemloh

I have made this PR with better error mapping of FFI errors. I’m not sure the interface given to developers are 100 %, so can you give it a review and then we can have a discussion if we can make some improvements.