Fix Issue 10717 - std.ascii.toLower and toUpper should return char instead of dchar and avoid me to use a bad cast(char)

It turns out it was incorrectly working for enum types.

New semantics are that enums are also accepted, and their OriginalType is returned.
rework toUpper/toLower unittests
Merge pull request #1581 from monarchdodra/asciiToUpper

Fix Issue 10717 - std.ascii.toLower and toUpper should return char inste...
Remove AA comparison from std.xml

The compiler has historically been doing a cast(void *) for AA compares,
which doesn't make much sense. Make it explicit to preserve existing
behaviour, until this module is replaced.
Merge pull request #1599 from donc/aa10381xml

Remove AA comparison from std.xml
Fix FunctionAttribute DDoc
Merge pull request #1600 from monarchdodra/FunctionAttributeDDoc

Fix FunctionAttribute DDoc