Add random numbers and fix some bugs.

Add random numbers and fix some bugs.

This patch adds random number support for UNSIGNED, plus fixes
two bugs, with array I/O where the type used to be set to BT_INTEGER,
and for division with the divisor being a constant.

gcc/fortran/ChangeLog:

	* check.cc (gfc_check_random_number): Adjust for unsigned.
	* iresolve.cc (gfc_resolve_random_number): Handle unsigned.
	* trans-expr.cc (gfc_conv_expr_op): Handle BT_UNSIGNED for divide.
	* trans-types.cc (gfc_get_dtype_rank_type): Handle BT_UNSIGNED.
	* gfortran.texi: Add RANDOM_NUMBER for UNSIGNED.

libgfortran/ChangeLog:

	* gfortran.map: Add _gfortran_random_m1, _gfortran_random_m2,
	_gfortran_random_m4, _gfortran_random_m8 and _gfortran_random_m16.
	* intrinsics/random.c (random_m1): New function.
	(random_m2): New function.
	(random_m4): New function.
	(random_m8): New function.
	(random_m16): New function.
	(arandom_m1): New function.
	(arandom_m2): New function.
	(arandom_m4): New function.
	(arandom_m8): New funciton.
	(arandom_m16): New function.

gcc/testsuite/ChangeLog:

	* gfortran.dg/unsigned_30.f90: New test.