support MaxScan in queries
add a test for max scan
mgo: optimize seeking to end of GridFS file
Fix windows compile issues due to import order
Tweak SetMaxScan documentation.
Merge branch 'rogpeppe-001-efficient-seek-end' into v2-dev.
Fix windows build issue due to sasl.h include order.

Merge from Valeri Karpov.
Merge README.md from tip.
MGO-35 add support for ServiceHostname for GSSAPI, test for ServiceName
MGO-35 address Gustavo's comments
MGO-35 fix a couple places where I missed Hostname => Host conversion
MGO-35 fix one more spacing issue
Make it possible to run tests on windows (with a little cygwin help)
Merge branch 'MGO-35' of https://github.com/vkarpov15/mgo into v2-dev

This adds support for ServiceHost on a GSSAPI authentication.
simple benchmarks
port benchmarks to gocheck
Merge Kyle's Raw benchmarks into v2-dev.
Tweak the Raw Iter benchmark to use c.N.
Couple more tweaks in the Raw Iter benchmark.
Add POC for windows Kerberos with SSPI