Define c_natural_high.

libraries/base/common/src/vhdl/common_pkg.vhd

@@ -51,6 +51,7 @@ PACKAGE common_pkg IS
   CONSTANT c_64                   : NATURAL := 64;
   CONSTANT c_128                  : NATURAL := 128;
   CONSTANT c_256                  : NATURAL := 256;
+  CONSTANT c_natural_high         : NATURAL := 2147483647;  -- = 2**31 - 1 = NATURAL'HIGH;
   
   -- widths and sizes
   CONSTANT c_halfword_sz          : NATURAL := 2;