I am all in favor of doing this. I never import the std namespace into my projects. I am pretty sure most C++ programmers frown on that and it's another amanteur hour thing to do so in my mind, so a huge thumbs up on this from me.

I defer to more senior project members such as deadalnix and freetrader on this one to actually approve this change -- but you got my vote, if that counts.

@AtlasShrugging re: your Test Plan question:

As a bare minimum when you touch the code, you should specify that the unit tests are run (make check)
If the change is functional, you may want to add running of the regression tests (qa/pull-tester/rpc-tests.py)
Have a look at the commit history for more examples.

When a change requires a test that cannot be automated, then specify the test steps, conditions, input data and expected outputs as clearly as possible so the next person has a good chance to reproduce the test without having to ring you up :-)

p.s. You can edit the summary and test plan of the Diff as you need.
In this case 'make check' is fine for tests and let the summary just describe the changes you made, briefly.
If the Diff title is enough to express that, just use 'as described' for the summary.