This replaces calls to Esize or RM_Size for standard integer types with
their value, uses Standard_Long_Long_Unsigned directly in one case and
Standard_Long_Long_Integer in another case, and changes the recently
added Narrow_Large_Operation to use Uint instead of Nat for sizes.

No functional changes (except maybe in a corner case on 32-bit targets).

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* exp_ch4.adb (Expand_Array_Comparison): Reformat.
	(Expand_Concatenate): Use standard size values directly and use
	Standard_Long_Long_Unsigned instead of RE_Long_Long_Unsigned.
	(Expand_Modular_Op): Use Standard_Long_Long_Integer in case the
	modulus is larger than Integer.
	(Expand_N_Op_Expon): Use standard size value directly.
	(Narrow_Large_Operation): Use Uint instead of Nat for sizes and
	use a local variable for the size of the type.
	(Get_Size_For_Range): Return Uint instead of Nat.
	(Is_OK_For_Range): Take Uint instead of Nat.