Branch pruning around IF function calls to avoid resolution of every branches

Calculation engine was resolving every function by first resolving its arguments
including IFs, this was causing significant over evaluation when IFs were used
as it meant for every case to be evaluated.

Introduce elements to identify ifs and enable better branch resolution
(pruning). We tag parsed tokens to associate a branch identifier to them.

Closes #844

Author: frantzmiccoli

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - When <br> appears in a table cell, set the cell to wrap [Issue #1071](https://github.com/PHPOffice/PhpSpreadsheet/issues/1071) and [PR #1070](https://github.com/PHPOffice/PhpSpreadsheet/pull/1070)
 - Add MAXIFS, MINIFS, COUNTIFS and Remove MINIF, MAXIF - [Issue #1056](https://github.com/PHPOffice/PhpSpreadsheet/issues/1056)
 - HLookup needs an ordered list even if range_lookup is set to false [Issue #1055](https://github.com/PHPOffice/PhpSpreadsheet/issues/1055) and [PR #1076](https://github.com/PHPOffice/PhpSpreadsheet/pull/1076)
+- Improve performance of IF function calls via ranch pruning to avoid resolution of every branches [#844](https://github.com/PHPOffice/PhpSpreadsheet/pull/844)
 
 ### Fixed