Change "8146793: logStream::write re-formats string" introduced an unconditional usage of the 'va_copy' macro which is not known to MSVC versions prior to VS2013.

The HotSpot code base already uses the 'va_copy' macro in jni.cpp with a guard against it being undefined.

This change will move the conditional guard and redefinition of 'va_copy' from jni.cpp to globalDefinitions_visCPP.hpp to make it available in all HotSpot source files.