use (void) instead of unused variable

$ ack -A1 "Make an unused local variable to avoid warning" src/
src/share/vm/prims/jvm.cpp
2814: // Make an unused local variable to avoid warning from gcc 4.x compiler.
2815- size_t count = ::write(defaultStream::output_fd(), s, (int)strlen(s));

src/share/vm/utilities/ostream.cpp
549: // Make an unused local variable to avoid warning from gcc 4.x compiler.
550- size_t count = fwrite(s, 1, len, _file);
--
599: // Make an unused local variable to avoid warning from gcc 4.x compiler.
600- size_t count = ::write(_fd, s, (int)len);