Fix Issue 4374 - Required do-while ending semicolon

Deprecation -> Error
Merge pull request #3929 from yebblies/issue4374

Issue 4374 - Required do-while ending semicolon
[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