Removed unused code, symbols
Drop NULs and process entire IMAP line

Discovered while working on Turkish UTF-8 bug, technically the IMAP
Deserializer was missing two things: (a) NUL is never allowed in an
IMAP line, even if the string is quoted, and so it should be dropped
rather than processed and cause potential issues, and (b)
DataInputStream will read to EOL, potentially leaving embedded NULs in
the line, meaning the old code would stop without processing the
entire IMAP response.

Although no server has been reported with these issues, I felt it
important to get this right as a defensive measure.