i386: Adjust emulated integer vector mode multiplication costs

i386: Adjust emulated integer vector mode multiplication costs

Returned integer vector mode costs of emulated modes in
ix86_multiplication_cost are wrong and do not reflect generated
instruction sequences.  Rewrite handling of different integer vector
modes and different target ABIs to return real instruction
counts in order to calcuate better costs of various emulated modes.

gcc/ChangeLog:

	* config/i386/i386.cc (ix86_multiplication_cost): Correct
	calcuation of integer vector mode costs to reflect generated
	instruction sequences of different integer vector modes and
	different target ABIs.