Enable dependence-analysis check to be ignored in ParallelLoopTrans

[arporter]

Currently the validate method of ParallelLoopTrans always uses the dependence analysis to check for loop-carried dependencies. However, there are occasions when a user will want to ignore the results of this (e.g. a loop that writes to an indirectly-accessed array but the user knows that each location is only written once). We need to implement support for an option to disable this check.