Don't use -Wextra on older gcc.
Don't use -Wextra on older gcc.

Check for -Wno-missing-field-initializers,
gcc without it would be too noisy.

ifduyue/libusual,rabbitt/libusual,markokr/libusual,ifduyue/libusual,rabbitt/libusual,rabbitt/libusual,markokr/libusual,mgjv/libusual,mgjv/libusual,mgjv/libusual,markokr/libusual,mgjv/libusual,markokr/libusual,rabbitt/libusual,ifduyue/libusual,ifduyue/libusual