Merge pull request #2707 from 9rnsr/fix11404

Issue 11404 - ICE on using TypeTuple for AA values
Merge pull request #2711 from 9rnsr/fix11424

[REG2.064a] Issue 11424 - typedef on structs isn't caught
Merge pull request #2708 from 9rnsr/fix10015

Issue 10015 - Segfault on forward referencing a variable of templated struct
Merge pull request #2703 from 9rnsr/fix11226

Issue 11226 - Problems with typeof(null) and const
fix Issue 11291 - Disallow mutation of a const variable