Add the Z 'type' to the mangling ABI to denote internal symbols.

See discussion here: https://github.com/D-Programming-Language/druntime/pull/725

D already creates mangled names using the Z symbol for internal symbols, e.g.
_D3foo3Bar6__vtblZ for the virtual table for class foo.Bar. The ABI makes no
mention of these symbols. This pull request adds Z to the mangling ABI to make
these official symbols. The linked pull request implements that demangling.
Don't list anchor overloads in Jump-to links
fix Issue 13538 - Divide old C style syntax from D style grammar rule
fix Issue 13539 - Disallow optional template parameters with C-style syntax
Divide DeclaratorIdentifier to VarDeclaratorIdentifier and newly added AltDeclaratorIdentifier
update AA key requirements
.min for floating types is an error
use of invariant has been an error for a while
Merge pull request #671 from WalterBright/error-invariant

use of invariant has been an error for a while
Merge pull request #673 from WalterBright/dep-min

.min for floating types is an error
Merge pull request #628 from Poita/bug8578

Add the Z 'type' to the mangling ABI to denote internal symbols.
Merge pull request #664 from 9rnsr/fix_declaration

Issue 13538 & 13539 - Improve variable declaration grammar for old C style syntax
Merge pull request #632 from MartinNowak/bugList2.066

generate list of fixed bugs for 2.066 release
changelog for 2.066.1
remove beta notice
Merge pull request #674 from MartinNowak/2.066

changelog for 2.066.1
Merge branch '2.066' into merge2.066

Conflicts:
	changelog.dd
	index.dd
Merge pull request #675 from MartinNowak/merge2.066

merge 2.066
Bump Visual D version to 0.3.39
Merge pull request #646 from ntrel/anchor-overloads

[pending] Don't list name.N anchors in Jump-to links