They can actually be shared with multiple threads at the same time
safely as all functions requiring an immutable reference are
thread-safe.
OTOH TypeFind can't be shared safely between different threads as not
all implementations of the TypeFind struct are thread-safe.
Fixes clippy warnings, prevents confusing errors and is more consistent.
The Display trait provides a to_string() method by itself and FromStr
provides from_str().
There's a VideoTimeCode type that represents any kind of timecodes,
including invalid ones, and which allows to change each field
individually. And ValidVideoTimeCode that has all fields
validated and that can be used with most of the API.
In C, validation of the timecodes is left to the user and most functions
assert on getting passed valid timecodes.
