Check if jpeg_src_mem is already implemented using MEM_SRCDST_SUPPORTED
Check if jpeg_src_mem is already implemented using MEM_SRCDST_SUPPORTED

Additionally change the signature of jpeg_src_mem to match the one provided
by libjpeg-turbo.

deskvox/deskvox,deskvox/deskvox,deskvox/deskvox,deskvox/deskvox,deskvox/deskvox