Treat warnings as error and fix most level 4 warnings in the breakpad windows client projects.

Some of the lint errors in the files touched by this change were also fixed.

BUG=533
Review URL: https://breakpad.appspot.com/601002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1189 4c0a9323-5329-0410-9bdc-e9ce6186880e