Fix Issue 10682 - [ICE](cgcod.c line 1561) with ^^ operator

The backend can't handle a shift expression with a ulong rhs, so simulate the cast that is usually added by semantic.
fix bugs found by valgrind
remember errors
Fixes Issue 10990 - getUnitTest trait does not work with module import.
Fix issue 10991 - Implement __traits(getVirtualIndex).

Minor tweaks to __traits(getVirtualIndex).
Add unit test for __traits(getVirtualIndex).

Added additional test for final overrides.

Fixed formatting for virtual index test.
foreach range uses same logic as ?: for type deduction
Added another test case for char..char
Formatting: moved else block to separate line.
Another incorrect brace fix.
refactor: combine disparate semanticRun's
Merge pull request #2508 from WalterBright/valgrind

fix bugs found by valgrind
Added another test case for wchar..wchar
Merge pull request #2532 from WalterBright/refactor-semanticRun

refactor: combine disparate semanticRun's
Merge pull request #2531 from WalterBright/errorprop

remember errors
fix Issue 9073 - In manifest constant initializer, && and || should evaluate their operands lazily.
fix Issue 10998 - compile-time postblit call check is incorrectly suppressed

In the pull request #1801, I had forgot to remove the *ungag* code. That was caused the incorrect gagging regression.
[trivial] fix fail341.d mistake

AFAICS, `@nocall` is a mistake of `@disable`.
Fix issue 10858 CTFE wrong array of pointers

Pointer comparison should be based on rvalues, not lvalues.
That bug was also hiding three latent wrong-code bugs.
fix Issue 10980 - static initialization of immutable structs with disabled postblit fails