Fix usage of snprintf for MSVC

Older versions of MSVC don't have a snprintf functions. Some files
were already working around that, but not all of them. Instead of
copying the logic into every file, I centralize it into a new
stdio.h wrapper file and make other files include that.

BUG=
R=mark@chromium.org

Review URL: https://codereview.chromium.org/1602563003 .

Patch from Pavel Labath <labath@google.com>.

src/processor/logging.cc

@@ -35,20 +35,16 @@
 
 #include <assert.h>
 #include <errno.h>
-#include <stdio.h>
 #include <string.h>
 #include <time.h>
 
 #include <string>
 
+#include "common/stdio.h"
 #include "common/using_std_string.h"
 #include "processor/logging.h"
 #include "processor/pathname_stripper.h"
 
-#ifdef _WIN32
-#define snprintf _snprintf
-#endif
-
 namespace google_breakpad {
 
 LogStream::LogStream(std::ostream &stream, Severity severity,