Add instructions of RC opcode format.
Add helper for mul, sha, absdif with signed saturation on overflow.
Add helper for add, sub, mul with unsigned saturation on overflow.
Add microcode generator functions:
    * gen_add_CC, which calculates the carry bit.
    * gen_addc_CC, which adds the carry bit to the add and calculates the carry bit.
    * gen_absdif, which calculates the absolute difference.
    * gen_mul_i64s/u, which mul two 32 bits val into one 64bit reg.
    * gen_sh_hi, which shifts two 16bit words in one reg.
    * gen_sha_hi, which does a arithmetic shift on two 16bit words.
    * gen_sh_cond, which shifts left a reg by one and writes the result of cond into the lsb.
    * gen_accumulating_cond, which ands/ors/xors the result of cond of the lsbs
      with the lsb of the result.
    * gen_eqany_bi/hi, which checks ever byte/hword on equality.
Signed-off-by: NBastian Koppelmann <kbastian@mail.uni-paderborn.de>
Reviewed-by: NRichard Henderson <rth@twiddle.net>