Deprecate InputRange source for OutputRanges

An output range for E won't be automatically an output range for [E]
anymore. The same, an output range for [E] won't be automatically an
output range for E. Automatic E <-> [E] conversion seems to be a nice
feature at first glance, but it causes much ambiguity.

1) If I want that my output range accepts only UTF-8 strings but not
single characters (because it could be only part of a code point and
look like broken UTF-8 without the remaining code units), I can't do it
because an OutputRange(R, E) can't distinguish between char and string.

2) Here is an example from 2013:

import std.range;
import std.stdio;
Appender!(const(char)[][]) app;
put(app, "aasdf");
put(app, 'b');
writeln(app.data);

This outputs: ["aasdf", "\0"].
Whether it is a common case or not, such code just shouldn't compile.

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