Exclude sandbox/linux from SpamLogging check and restrict printf check.

1. Restrict the printf check to stdout / stderr

2. sandbox/linux uses printf and fprintf for good reason in a few places.
None of these would ever spam Chrome's stderr.

- Tests inside sandbox/linux have to run within their own small test
framework (so that they can run each in their own process). In this
framework, fprintf(stderr, XX) can be used to fail a test.

- The setuid sandbox is its own command line executable. It uses fprintf.

- A small number of tests (2), use fprintf to report kernel status while
running the test. It's extremely useful.

- The code generator in the BPF compiler was developped without base/
originally. It uses fprintf in a debug mode to print the assembled
program. This will only trigger on the equivalent of "compilation errors".

R=maruel@chromium.org, thakis@chromium.org

Review URL: https://codereview.chromium.org/89073002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237624 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237624