(shift_cost): Now a vector.

(shiftadd_cost): New vector for cost of (N * a + b) instructions.
(shiftsub_cost): New vector for cost of (N * a - b) instructions.
(lea_cost): Removed.
(init_expmed): Initialize new vectors.  Use ASHIFT, not LSHIFT.
Remove code initializing lea_cost.
(enum alg_code): New definition.
(synth_mult): Rewrite for better algorithms and faster operation.
(expand_mult): Rewrite code for constant multiplication.

From-SVN: r3735