Wrong charset used in creating search terms when server supports UTF8

[ZhongXiaoHong]

there is a bug ,when i search subject with Chinese character such as “OA系统”. The log print :https://github.com/ZhongXiaoHong/mail/blob/master/bad_comand.txt
The reason for this is that the Chinese character “OA系统” is regarded as ASSCII when the program get the byte array.
see the source code: com.sun.mail.imap.protocol.SearchSequence#subject(SubjectTerm term, String charset)
protected Argument subject(SubjectTerm term, String charset) throws SearchException, IOException { Argument result = new Argument(); result.writeAtom("SUBJECT"); result.writeString(term.getPattern(), charset); return result; }

com.sun.mail.iap.Argument#writeString(java.lang.String, java.lang.String)

public Argument writeString(String s, String charset) throws UnsupportedEncodingException { if (charset == null) { this.writeString(s); } else { this.items.add(new AString(s.getBytes(charset))); } return this; }

com.sun.mail.iap.Argument#writeString(java.lang.String)

public Argument writeString(String s) { this.items.add(new AString(ASCIIUtility.getBytes(s))); return this; }

[jmehrens]

This PR quotes UTF8 strings in SEARCH which, if I'm reading the RFC 3501 and RFC 6855 correctly is not allowed. If I modify the IMAPSearchTest I see:

B3 SEARCH SUBJECT "’系统" ALL

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