fix Issue 13400 - Linking problems with bigints and std.functional.memoize
Fix Issue 2656 - Remove octal literals

Deprecation -> Error
[Refactoring] Remove unused flag 0x100 in Type::toDecoBuffer
[Refactoring] Directly handle OutBuffer in Mangler
[Refactoring] Move type mangling code into mangle.c
[Refactoring] Move expression mangling code into mangle.c
Merge pull request #3916 from yebblies/issue2656

Issue 2656 - Remove octal literals
When allocating a struct with "new", do not pass the pointer type info to the runtime, but the struct type info.
Merge pull request #3933 from 9rnsr/refactor_mangle

[Refactoring] Move almost mangling code into mangle.d
Merge pull request #3935 from rainers/fix_13404

Issue 13404 - heap-allocating a struct passes TypeInfo_Pointer to the GC, not TypeInfo_struct
Merge pull request #3932 from 9rnsr/fix13400

[REG2.067a] Issue 13400 - Linking problems with bigints and std.functional.memoize