README.md: Revise unsupported platforms/compilers note.
README.md: Revise unsupported platforms/compilers note.

csuideal/log4cplus,csuideal/log4cplus,csuideal/log4cplus,ccpaging/log4cplus,ccpaging/log4cplus,ccpaging/log4cplus,csuideal/log4cplus,ccpaging/log4cplus