[Refactoring] Clean up syntaxCopy functions

Dsymbol, Statement, Expression, Type, and Initializer.
Merge pull request #3886 from 9rnsr/refactor_syntaxCopy

[Refactoring] Clean up syntaxCopy functions
[Refactoring] Remove unused field GotoStatement::fd
[Refactoring] Reorder fields in LabelStatement
[Refactoring] Improve the look of code in `GotoStatement::semantic()` and `LabelStatement::semantic()``
Remove unused storage class STCcomdat
Merge pull request #3887 from 9rnsr/refactor_unused

[Refactoring] Remove unused field GotoStatement::fd
Merge pull request #3888 from schuetzm/remove-unused-STCcomdat

Remove unused storage class STCcomdat
replace stray tabs with spaces
Merge pull request #3890 from rainers/detab

replace stray tabs with spaces