Fix buffer overrun in wxPrintf() format parsing code.

Parsing a format specifier with an asterisk (e.g. "%.*s") for the 64th
argument of wxPrintf() resulted in a buffer overrun as the check for the
maximal number of arguments didn't break out from the right loop.

Fix this by inserting an extra check for this.

Thanks Coverity for finding this one.

include/wx/private/wxprintf.h

@@ -870,6 +870,11 @@ struct wxPrintfConvSpecParser
 
                     spec = &specs[nargs];
                 }
+
+                // If we hit the maximal number of arguments inside the inner
+                // loop, break out of the outer one as well.
+                if ( nargs == wxMAX_SVNPRINTF_ARGUMENTS )
+                    break;
             }