Consider safety of almost all API calls

[kenz-gelsoft]

Consider safety of almost all API calls

[kenz-gelsoft]

Marking following methods unsafe may make it programmer's responsibility

• destroy()
• any close operations of wxWindows (which results destroying wx managed pointers)

I think this is a reasonable compromise than other approaches like:

• Programmer checks all wx calls is safe by:
  • Making all calls returns Result and fallible
  • Checking every reference to wx-managed pointer by get()ing from wx::WeakRef.

Those approaches will increase run-time overhead unreasonablly. As a Rust library, this isn't desirable.

Providing unsafe and performant variants to whole APIs doubles the work for binding.