Bug: unittest line 55 in std.encoding was disabled by version(none)

Rationale: Re-enabling unittest at line 55 results in failure. 

Fix: At line 1059  inside template EncoderInstance(CharType : char). 

Current version:

    dchar decodeReverseViaRead()()

    {

        auto c = read;
....


Fixed version:
    dchar decodeReverseViaRead()()
    {
        dchar c = read;
....

Its obvious after failure point is pinned, even if not knowing the exact specs, as decodeReverseViaRead must return a dchar, and variable c accumulates left shifted bits in the loop, same as the nearby safeDecodeViaRead method. In UTF-8,the auto c = read makes a char type only (thank you zerobugs debugger), so high bits put in c are thrown away, and function may return character 0. Re-enabled unittest code ran succesfully after above fix.