Detab std.array.
Fixes Issue 4287 - Implement concat-assign operator for Appender.
Specialize textImpl for 1-argument case.
Fix broken example.

That one example wouldn't compile, so I fixed it.
Merge pull request #1108 from AndrejMitrovic/Fix4287

Issue 4287 - Implement concat-assign operator for Appender.
Merge pull request #1121 from 1100110/patch-2

Fix broken example in std.stdio;
Merge pull request #1115 from AndrejMitrovic/SpeedUpText

Specialize textImpl for 1-argument case.
Fixup Pull1555 - Zero-arg text() should return null string.
Merge pull request #1122 from AndrejMitrovic/Fixup1115

Fixup Pull1555 - Zero-arg text() should return null string.