change firstByteMark to unsigned to prevent constant overflow warning
change firstByteMark to unsigned to prevent constant overflow warning


git-svn-id: ad8080c0dac9953171417b882a4cafa638f6aa75@33 e3330c51-1366-4df0-8b21-3ccf24e3d50e

FSMaxB/mcJSON,splbio/cJSON,FSMaxB/mcJSON,mirco/cjson