fix Issue 9434 & 9435 - regression(head): forward reference error

test/compilable/test9434.d and test9435.d are mutually dependent.
Merge pull request #1589 from 9rnsr/fix9435

Issue 9435 - regression(head): forward reference error
fix Issue 9244 - union containing pointers not allowed
Merge pull request #1591 from WalterBright/b46

fix Issue 9244 - union containing pointers not allowed
remove unnecessary #include's
Merge pull request #1592 from WalterBright/b47

remove unnecessary #include's
lurch towards const correctness
Merge pull request #1593 from WalterBright/b48

lurch towards const correctness
fix Issue 9436 - enum cannot be forward referenced with cyclic imports and mixin
Array doesn't need to be an Object
fix Issue 9439 - CTFE ICE: calling member function after "incorrect this" error
Merge pull request #1596 from WalterBright/b49

Array doesn't need to be an Object
< and > are magic only if generating HTML
Add `bool isv` parameter to Dsymbol::mangle()
fix Issue 8847 - voldemort + inout confuses "is"
Merge pull request #1594 from 9rnsr/fix9436

Issue 9436 - enum cannot be forward referenced with cyclic imports and mixin
Merge pull request #1597 from 9rnsr/fix9439

Issue 9439 - CTFE ICE: calling member function after "incorrect this" error
Merge pull request #1599 from andralex/master

< and > should be magic only when generating HTML
remove old dead code
Merge pull request #1602 from WalterBright/refactor2

remove old dead code