[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 #3933 from 9rnsr/refactor_mangle

[Refactoring] Move almost mangling code into mangle.d