fortran: calculate elements of a subarray using a provided stride value

fortran: calculate elements of a subarray using a provided stride value

The stride value can be a positive or negative integer, but may
not be zero.  If no stride is provided, use the default value
1 to print all elements inside the range.

1| program prog
2|   integer :: ary(10) = (/ (i, i=1, 10) /)
3| end program prog

(gdb) print ary(1:10:2)
$3 = (1, 3, 5, 7, 9)

2013-11-27  Christoph Weinmann  <christoph.t.weinmann>

	* eval.c (value_f90_subarray): Add range size calculation
	for stride based ranges, and evaluation of user stride
	parameters.  Add check for matching user input to array
	bounds.
	* valops.c (value_slice): Add call parameter with default
	stride value for calling value_slice_1.
	* valops.c (value_slice_1): Add function parameter for
	stride length in the return subarray.  Calculate array
	elements based on stride value.
	* value.h: Add stride parameter to declaration of
	value_slice_1.

Signed-off-by: Christoph Weinmann <christoph.t.weinmann@intel.com>