PR fortran/30834

	* arith.c (complex_pow): Rewrite to handle large power.
	(gfc_arith_power): Handle large power in the real and integer
	cases.

	* gfortran.dg/integer_exponentiation_3.F90: New	test.
	* gfortran.dg/integer_exponentiation_4.f90: New test.
	* gfortran.dg/integer_exponentiation_5.F90: New test.

From-SVN: r123154