* need refactor

* this can eliminate masking the result of subtraction with 0xff or
  0xffff

* Treating (dsrc1 + CF) as whole, which is introduced in 051786, is
  wrong. (dsrc1 + CF) may generate carry bit. Treating them as whole
  will miss such carry.
* Also we should introduce a new rtl register s2 to compute the CF of
  adc/sbb.

* pass eflagstest

* other operands can be re-computed

* now printf() can output correctly

* it seems that printf() can not output correctly, there is something
wrong with CC computation for adc/sbb

* Now we treat (dsrc1 + CF) as whole and compute CF/OF based on it.
  Whether this is correct is still to be checked.

* if ddest == dsrc1, the computation of flags will be wrong

* this makes it easier to perform constant propagation

* byte/word register accessing still need data movement

* we can not access runtime value at the translation time
* fix by guarding the shift amount with mask in the interpreter

* if it is the case, should not perform the shift
* also note that shifting 32 bit on a 32-bit value is UB

* now the set of API to abstract the behavior of different ISAs are
  listed in include/isa.h
* ISA-dependent structure and macro definitions used by non-ISA code are
  listed in include/$ISA.h