binlog streamer: improved handling of premature EOF

If mysqlbinlog ends without seeing a COMMIT, it inserts a fake ROLLBACK
at the end of the stream.
The binlog streamer sees a ROLLBACK and discards all statements up to
that point, and resumes streaming from the next position, which it
should not do.
It should instead retry the entire transaction.
But, we need to differentiate between real rollbacks and the fake ones.
So, this CL looks for the end of log file marker instead, which comes
before the ROLLBACK.

Also fixed a flakyness in queryservice test.
parser: Value->Val
parser: more renames
parser: macro-ise strings

Also grouped functions that are meant to satisfy interfaces close to
those interfaces.
parser: standardadize on naming of dummy functions
parser: DDL.Action int -> string
parser: more macro-isation of strings
parser: add basic benchmarks
parser: removed panic error hadling from token.go
parser: all references to Node replaced
parser: RIP Node!
parser: files renamed.
parser: cosmetic changes
queryservice: remove sensitive mode flag.

Sensitive mode turned out to be not very useful, and there was no easy
way to keep the feature maintainable. It's better to get rid of this
feature that was complicating code without adding much value.
bson: reduce DefaultBufferSize from 16K to 1K

The default buffer size is actually too high for generally average
payloads. Reducing to a more reasonable 1K.

benchmark                    old ns/op     new ns/op     delta
BenchmarkMarshal             26888         16526         -38.54%
BenchmarkUnmarshal           18394         18568         +0.95%
BenchmarkEncodeField         4852          4963          +2.29%
BenchmarkEncodeInterface     2964          3136          +5.80%

For bsonrpc, we already override this value to be 4K. So, this shouldn't
affect our performance.
Merge branch 'parser'
Merge branch 'master' of github.com:youtube/vitess
Global flag injection for integration tests