(mul_cost, div_cost): New variables.

(mul_widen_cost, mul_highpart_cost): New variables.
(init_expmed): Init new variables.
(expand_mult_highpart): New argument, MAX_COST.
Use new argument in several places.  Simplify code that tries
widening multiply variants.
(expand_divmod): New variables MAX_COST, EXTRA_COST.
Initialize MAX_COST dependent on REM_FLAG.
Calculate and pass cost in all calls of expand_mult_highpart.

From-SVN: r8868