Minimal change to support for CHAR and VARCHAR types

This is a quick fix to support the above two types added in Impala 2.0.
The thrift definitions in the Impala 2.0 branch have too much to use the
script thrift/process_thrift.sh without making much larger changes. So
instead of using the process script, I manually editied the
cli_service.thrift to include the new types. This is much easier but
means the next time process_thrift is used, these changes will be lost.
Merge pull request #32 from caseyching/master

Minimal change to support for CHAR and VARCHAR types
Added support for HiveServer2 protocol V6

In preparation for Impala 2.0
Added VARCHAR and CHAR after accidental omission
Merge pull request #36 from cloudera/hs2v6

Implement suport for HiveServer2 protocol V6, for Impala 2.0
Fix UDF regressions. Fixes #29. Add UDF exec tests

* Pulled in a newer `udf.h`

* Impala UDF named structs now pulled out of precompiled module with dummy fn

* UDFs now link a fresh precompiled module into each UDF

* Split C++ code into string implementations and type spec; updated `Makefile` and `setup.py`

* ImpalaContext now cleans up UDFs and UDAs

* Switched UDF modules to absolute imports