optimize DCS put/unhook

[jerch]

Currently the DCS handling of the parser works in 3 different steps:

• HOOK: activates a certain subparser and announces escape sequence parameters to it
• PUT: payload for the subparser, might be called multiple times with payload chunks
• UNHOOK: tells the subparser thats the DCS command is about to finish

Currently all DCS commands we support have rather short payload and their parsers do their business in unhook. This leads to unnecessary data copy of the last payload chunk, that cannot be evaluated before unhooking.

Solution: Skip PUT for the last payload chunk and transfer it with UNHOOK directly.

[jerch]

Closing this issue as it will not save much, but make the parser much more complicated.