DRILL-1470 : cast into varchar should recognize the length parameter in varchar. Fix casting function implementation: the length parameter should mean # of chars, not # of bytes.

New unit test case to verify the result from cast function.

Fix bug in cast into varchar. When target length = 0, it means we want to keep the input .

code clean up.

Include change for varbinary cast as well.
DRILL-1592: Detect drillbit failure and cancel the affected running queries.

Revise code based on review comments.

Revise code based on comments: only track the newly dead drillbits.

Remove some debug msg.

Minor code change based on review comments.

clean up.

add comment. Clear listeners when drillbit is unregistered from CC.

Minor code change from review comments.