Fortran: do not frontend-optimize MINLOC/MAXLOC for character arrays

gcc/fortran/ChangeLog:

	PR fortran/104811
	* frontend-passes.cc (optimize_minmaxloc): Do not attempt
	frontend-optimization of MINLOC/MAXLOC for character arrays, as
	there is no suitable code yet for inline expansion.

gcc/testsuite/ChangeLog:

	PR fortran/104811
	* gfortran.dg/minmaxloc_16.f90: New test.