Re-implement Statement::apply in terms of Visitor
Move Statement::inlineScan into inline.c
Move Expression::inlineScan into inline.c
Move Dsymbol::inlineScan into inline.c
Merge pull request #3111 from yebblies/sapplyvisitor

[DDMD] [refactor] Re-implement Statement::apply in terms of Visitor
Merge pull request #3164 from yebblies/inlinescan

[DDMD] [refactor] Move inlineScan into a visitor class in inline.c