Expand BinAssignExp macros in expression.h
fix Issue 11226 - Problems with typeof(null) and const
fix Issue 11404 - ICE on using TypeTuple for AA values
fix Issue 10015 - Segfault on forward referencing a variable of templated struct
fix Issue 11424 - typedef on structs isn't caught

It should be caught even if the typedef keyword usage is meaningless.
fix Issue 11426 - Reinterpret element-wise array initializing should be rejected
Remove Tascii and replace with Tchar
Remove redundant extern declarations.
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
Merge pull request #2678 from 9rnsr/fix11291

Issue 11291 - Disallow mutation of a const variable
Merge pull request #2422 from yebblies/expandmexp

[DDMD] Expand BinAssignExp macros in expression.h
Merge pull request #2713 from yebblies/mtypecleanup

Mtypecleanup
Merge pull request #2712 from 9rnsr/fix11426

[REG2.061] Issue 11426 - Reinterpret element-wise array initializing should be rejeted
Do not pass string literals to c variadic functions
Fix fieldinit typo
Merge pull request #2715 from yebblies/fieldinit

[DDMD] Fix fieldinit typo