stringhelper.cxx: Simplify toupper_func and tolower_func, always tolower() and toupper() from std namespace.
stringhelper.cxx: Simplify toupper_func and tolower_func,
always tolower() and toupper() from std namespace.

hunter-packages/log4cplus,csuideal/log4cplus,csuideal/log4cplus,ccpaging/log4cplus,csuideal/log4cplus,hunter-packages/log4cplus,ccpaging/log4cplus,hunter-packages/log4cplus,ccpaging/log4cplus,hunter-packages/log4cplus,csuideal/log4cplus,ccpaging/log4cplus