Fix#4415. We store the rarely-used property Drawing/Shadow/Alpha as an integer representing the percentage. Excel also stores it as an integer, but multiplies it by 1,000, so we divide by 1,000 when we read this value. This can, and in the case of the issue at hand does, leave a fractional portion. Php has deprecated passing a float with a fractional portion to an int argument, so the reporter saw a deprecation message. This is easily fixed.
Dealing mostly with mixed variable type. In a great many cases, problems can be resolved replacing `getValue` with `getValueString` or `getCalculatedValue` with `getCalculatedValueString`.
When I implemented IgnoredErrors (PR #3508), I dealt only with those that I understood well enough to come up with an example. I finally found an example for FormulaRange in the wild, so this PR adds it. Still unsupported are `calculatedColumn`, `emptyCellReferece`, `listDataValidation`, and `unlockedFormula`.
For an overview of why this is desired (and ways that people have coped with its absence), see issue #2900 and issue #4048; also PR #4043 which will be superseded by this PR.
The list of Excel functions is moved from Calculation/Calculation to its own member. I believe that it is done in a way that will not cause big complications to two experiments from @MarkBaker (PR #2714 and PR #2734). I believe it is also done in such a way that further refactoring of Calculation can follow this model.
Custom functions can be added or removed from the function list. You cannot add a function if it already exists in the list, and you cannot remove a non-custom function from the list. They will, of course, not be understood by Excel if written to a spreadsheet; the use case is mainly using the Calculation engine outside of spreadsheet context.
Fix#4381. The report refers to COUNTIF, but AVERAGEIF and SUMIF, which are implemented in the same module, exhibit the same behavior. (There may be others, but, for now, I will just fix those 3.)
Most methods which implement Excel functions should accept mixed arguments, so that they won't throw exceptions when calculated. Of course, MS often doesn't give much guidance as to how unexpected arguments should be handled. It at least seems clear that MS will often substitute #REF! for some arguments, and will return #REF! as the result in such cases. My test indicates that a formula using, say, #DIV/0! in lieu of #REF! will cause Excel to deem the spreadsheet corrupt. So, I think I am just going to deal with #REF! and let other unexpected values continue to throw exceptions.