Remove buggy special case in irange::invert [PR109934].

Remove buggy special case in irange::invert [PR109934].

This patch removes a buggy special case in irange::invert which seems
to have been broken for a while, and probably never triggered because
the legacy code was handled elsewhere, and the non-legacy code was
using an int_range_max of int_range<255> which made it extremely
likely for num_ranges == 255.  However, with auto-resizing ranges,
int_range_max will start off at 3 and can hit this bogus code in the
unswitching code.

	PR tree-optimization/109934

gcc/ChangeLog:

	* value-range.cc (irange::invert): Remove buggy special case.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/pr109934.c: New test.