Fix issue 12771 - Variant opIndex for static arrays is not implemented.
Shorten array checks to isArray
add byCodeunit, byChar, byWchar and byDchar to std.utf
Merge pull request #2188 from Kapps/fix12771

Fix issue 12771 - Variant opIndex for static arrays is not implemented.
Merge pull request #2043 from WalterBright/byChar

add byCodeunit, byChar, byWchar and byDchar to std.utf