Add support for variable of primitive data type 'bit'

Verilog allows user to define variables of primitive types. The patch
adds support for defining variables of type 'bit'. The data type 'bit'
is the only primitive data type which supports defining ranges.

Signed-off-by: Prasad Joshi <prasadjoshi124@gmail.com>

parse.y

@@ -605,6 +605,12 @@ block_item_decl
 		  if ($1) delete $1;
 		}
 
+	| attribute_list_opt K_bit unsigned_signed_opt range_opt
+	  register_variable_list ';'
+		{
+			pform_set_net_range($5, $4, $3, IVL_VT_BOOL);
+			if ($1) delete $1;
+		}
   /* Integer atom declarations are simpler in that they do not have
      all the trappings of a general variable declaration. All of that
      is implicit in the "integer" of the declaration. */

vvp/vpi_signal.cc

@@ -515,6 +515,7 @@ struct __vpiSignal* vpip_signal_from_handle(vpiHandle ref)
 	  case vpiShortIntVar:
 	  case vpiIntVar:
 	  case vpiLongIntVar:
+	  case vpiBitVar:
 	    return (struct __vpiSignal*)ref;
 
 	  default: