PR31314, chew crashing on use of uninitialized value

The "drop" call in wrap_comment already increments pc.  Defining DOCDD
in proto.str is a warning fix.

	PR 31314
	* chew.c (wrap_comment): Don't increment pc.
	* proto.str (DOCDD): Define.

bfd/doc/chew.c

@@ -541,8 +541,6 @@ wrap_comment (void)
 
   overwrite_string (tos - 1, &out);
   drop ();
-
-  pc++;
 }
 
 /* Mod tos so that only lines with leading dots remain */

bfd/doc/proto.str

@@ -166,6 +166,7 @@
 : SUBSUBSECTION ignore ;
 : INODE ignore ;
 : DESCRIPTION ignore ;
+: DOCDD ignore ;
 : ENDDD EXTERNAL ;
 : FUNCTION EXTERNAL ;
 : INTERNAL_FUNCTION INTERNAL ;