More length restrictions in debugger protocol

More length restrictions in debugger protocol

Restrict the length of the textual representation of variable values that are sent over the debugger wire protocol. The full value can still be retrieved explicitly by the debugger client.
 
Committed: https://code.google.com/p/dart/source/detail?r=17517

[hausner, 2013-01-23 22:48:56]

This change generalizes the truncation idea from the last checkin, restricting
the length of any value. I would love to treat maps explicitly, like lists, but
we don't have an API for maps.

[srdjan, 2013-01-24 00:35:02]

lgtm

[hausner, 2013-01-24 00:54:23]

Thank you.