SERVER-8097 increment writebackSince on every request but GLE
Fix behavioral bugs in db.addUser js helper.

db.addUser() should not visibly mutate the input object.
db.addUser() should not require the 'roles' array to be nonempty.
Updated preprocessor directives to include BSD and Solaris
SERVER-7849: lower number of clients for debug builds and non-linux machines
Merge branch 'master' of git://github.com/mongodb/mongo