[prange] Do not trap by default on range dispatch mismatches.
The trap in the range-op dispatch code is really an internal debugging
aid, and only a temporary one for a few weeks while the dust settles.
This patch turns it off by default, allowing problematic passes to
turn it on for analysis.
gcc/ChangeLog:
* range-op.cc (TRAP_ON_UNHANDLED_POINTER_OPERATORS): New
(range_op_handler::fold_range): Use it.
(range_op_handler::op1_range): Same.
(range_op_handler::op2_range): Same.
(range_op_handler::lhs_op1_relation): Same.
(range_op_handler::lhs_op2_relation): Same.
(range_op_handler::op1_op2_relation): Same.