Ported from https://github.com/bitcoin/bitcoin/pull/17877.
Since Qt 5.5 there are means to register an enum type with the meta-object system (such enum still lacks an ability to interact with QSettings::setValue()
and QSettings::value()
without defined stream operators).
In order to reduce global namespace polluting and to force strong type checking, this PR makes BitcoinUnits::Unit
a scoped enum (typedef BitcoinUnits::Unit BitcoinUnit;
).
No behavior change.