Summary
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Add verbiage making explicit the behavior of the `Reader` methods read(char[] cbuf) when cbuf.length is zero and read(char[] cbuf, int off, int len) when len is zero.

Problem
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The behaviors of read(char[] cbuf) when cbuf.length is zero and read(char[] cbuf, int off, int len) when len is zero are not as completely specified as in the analogous `InputStream` methods.

Solution
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Add verbiage making explicit the behavior of the `Reader` methods read(char[] cbuf) when cbuf.length is zero and read(char[] cbuf, int off, int len) when len is zero.

Specification
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To the specification of `Reader::read(char[])` add the paragraph

```If the length of cbuf is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.```

and to that of `Reader::read(char[],int,int)` add the paragraph

``` If len is zero, then no characters are read and 0 is returned; otherwise, there is an attempt to read at least one character. If no character is available because the stream is at its end, the value -1 is returned; otherwise, at least one character is read and stored into cbuf.```