middle-end: check if target can do extract first for early breaks [PR113199]

middle-end: check if target can do extract first for early breaks [PR113199]

I was generating the vector reverse mask without checking if the target
actually supported such an operation.

This patch changes it to if the bitstart is 0 then use BIT_FIELD_REF instead
to extract the first element since this is supported by all targets.

This is good for now since masks always come from whilelo.  But in the future
when masks can come from other sources we will need the old code back.

gcc/ChangeLog:

	PR tree-optimization/113199
	* tree-vect-loop.cc (vectorizable_live_operation_1): Use
	BIT_FIELD_REF.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113199
	* gcc.target/gcn/pr113199.c: New test.