Syntax
#define INPUT_2BYTES(cinfo,V,action) \
MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
bytes_in_buffer--; \
V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
MAKE_BYTE_AVAIL(cinfo,action); \
bytes_in_buffer--; \
V += GETJOCTET(*next_input_byte++); )