Relax isPOD rules so ctors don't make structs non-POD
MODxxx is unsigned char, not unsigned
Issue 11503 - immutable return value from pure function implicitly converts to mutable.
Remove CallExp::implicitCastTo altogether.

The pure -> immutable case is checked in implicitConvTo as well,
and since it yields MATCHexact, the castTo() in
Expression::implicitCastTo is a no-op anyway.
Issue 11909 - Struct members and static arrays break pure function escape analysis (immutability violation).
Clarify traverseIndirections implementation.

No functional change intended.
Make traverseIndirections() return bool instead of int.
Add test case for issue 11969
Merge pull request #3144 from yebblies/MOD

[DDMD] MODxxx is unsigned char, not unsigned
fix Issue 11993 - typeof(this) in constraint of member function template should reflect method qualifier
Merge pull request #3150 from 9rnsr/fix11969

Add test case for issue 11969
Merge pull request #3151 from 9rnsr/fix11993

[REG] Issue 11993 - typeof(this) in constraint of member function template should reflect method qualifier
C++ mangle. Additional cases and tests for unix.

class mangle, volatile et c.
disable array passing test

disable static array arguments mangling.
disable a ctor mangling
Merge pull request #3116 from IgorStepanov/cppmangleunix

C++ mangle. Additional cases and tests for unix.
Fix some new D incompatibilities
Disable rtti
Move TypeInfo::toDt into a visitor class
Merge pull request #3152 from yebblies/ddmdpatch

[DDMD] Fix some new D incompatibilities