[X86] Split WriteIDiv into 8/16/32/64 implementations

[RKSimon]

Bugzilla Link	36930
Resolution	FIXED
Resolved on	May 08, 2018 07:42
Version	trunk
OS	Windows NT
Blocks	#31672 #36479 #36256
Fixed by commit(s)	rL331767

Extended Description

It's highly unlikely that a target can perform different sized integer divisions at the same rate, so why do we put them under the same scheduler class?

[RKSimon]

WriteIDiv was split at rL331767 - most of the Intel targets are overriding these classes at the moment so don't use the classes much (or at all), these need to be fixed on a case by case basis.

[RKSimon]

mentioned in issue #36479