Fix#3889. Fix#2464. After evaluating HYPERLINK function specifying cell address(es) rather than literal(s), the calculated hyperlink is attached to the wrong cell. I probably should have figured this out sooner - this is just another instance of the common problem of trying to assign a cell to a variable and then using the variable after a delay during which the "current" cell may have changed. The problem is resolved by storing the cell's worksheet and coordinate on entry to HYPERLINK, then restoring those before manipulating the hyperlink before returning to the caller.
An additional problem with hyperlinks is that assigning a new value to a cell has not cleared any hyperlink associated with the cell. This will now happen, if needed, whenever `setValue` or `setValueExplicit` is called.
A third problem is unaddressed. A (fairly unrealistic) formula like:
```php
$sheet->getCell('A4')->setValue('=LEN(HYPERLINK("http://www.example.com", "Example"))');
```
winds up attaching a hyperlink to the cell when its value is calculated, and it probably shouldn't. However, @TobiasBg reports in 2464 that Excel for Mac does the same thing, and I've just confirmed that Excel 365 on Windows does likewise. Furthermore, the hyperlink which Excel creates is not usable ("Cannot open the specified file"), whereas the link that PhpSpreadsheet creates is usable. So we're not doing any worse than Excel, and arguably doing better. I'm satisfied.
oleibman