Remove StrUtils.PosEx implementations, redirect to Pos.
...Because `Pos` is able to do the same for quite some time. Redundancy improves hardware reliability but software is another story.
Patch: [posex.patch](/uploads/ba4460219aad628fcd8fe6bc76ace314/posex.patch).
Also make `Offset` arguments [signed](https://docwiki.embarcadero.com/Libraries/Sydney/en/System.StrUtils.PosEx) and slightly improve `RPos*`.
issue