RFR 8073692: (cs) Inconsistent docs for CharsetDecoder.replaceWith and CharsetEncoder.replaceWith

[Ivan Gerasimov]

Hello!

It was noticed, that the javadoc for CharsetDecoder#replaceWith is 
missing the words about constraints on the length of the new replacement 
string [1].

Another small glitch is that the common part (of both encoder and 
decoder) of the 'newReplacement' param description is prepended to each 
specific description, so they read like that: "The replacement value The 
new replacement; ..."

Would you please help review the fix?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8073692
WEBREV: http://cr.openjdk.java.net/~igerasim/8073692/0/webrev/

Sincerely yours,
Ivan

[1] 
http://docs.oracle.com/javase/8/docs/api/java/nio/charset/CharsetDecoder.html#replaceWith-java.lang.String-