[NaCl SDK] When running "make debug", by default use "Debug".

You can still override this by specifying "make debug CONFIG=Release".

BUG=307719
R=jvoung@chromium.org, sbc@chromium.org

Review URL: https://codereview.chromium.org/26644004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228938 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228938
[NaClDocs] Some cleanup for the Running the SDK Examples page.

- More info about browser flags w.r.t. PNaCl.
- Consistently use pepper 31 instead of mostly pepper 28 with
  a sprinkle of pepper 31.
- Add some TODOs about some possible issues.
- Change indentation, seems to affect formatting.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3634
NOTRY=true

Review URL: https://codereview.chromium.org/27335005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228939 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228939