* refactor: prefer constexpr over enum for GUI_PAD values
* refactor: prefer constexpr over enum for PrefsDialog values
* refactor: prefer constexpr over enum for StatsDialog values
* refactor: use enum class for GtrUnicode types
* refactor: prefer constexpr over enum for BT peer msg codes
* refactor: use enum class for TrMakemetaResult
* refactor: prefer constexpr over enum for BT metadata message types
* refactor: use enum class for AwaitingBt
* refactor: use enum class for EncryptionPreference
* refactor: use enum class for TrFormat in rpcimpl
* refactor: prefer constexpr over enum for QApp intervals
* refactor: prefer constexpr over enum for tr_resume bitfields
* refactor: prefer constexpr over enum for Qt/TrFileModel bitfields
* refactor: remove obsolete TODO comment in announce-list
* (C++) Macros should not be used to define constants
* (C++) Memory should not be managed manually
* (C++) "void*" should not be used in typedefs, member variables, function parameters or return type
* (C++) When the "Rule-of-Zero" is not applicable, the "Rule-of-Five" should be followed
* (C++) "switch" statements should have "default" clauses
* (C++) "explicit" should be used on single-parameter constructors and conversiosn operators
* (C++) Non-const global variables should not be used
