[Refactoring] Remove unused code for 'symfile'
[Refactoring] Remove unnecessary memset for HdrGenState

It's already done in the default constructor.
[Refactoring] Remove unused fields in HdrGenState
[Refactoring] Remove HdrGenState::console
Add Nspace into Visitor
Add TemplateParameter and its derived classes into Visitor
Add Condition and its derived classes into Visitor
Add Parameter into Visitor
[Refactoring] Rename FLinit.init to forStmtInit
Merge pull request #3856 from 9rnsr/fix_visitor

Add Nspace and others into Visitor
Merge pull request #3857 from 9rnsr/refactor_unused

[Refactoring] Remove unused code around header generation
Slim up test cases for header generation
Merge pull request #3853 from 9rnsr/hdrgen_test

Slim up test cases for header generation
Merge branch 'master' of https://github.com/D-Programming-Language/dmd