message catalogs: fix comment lines, also remove linux hack in merge.c

According to the spec, blank lines in message catalogs or lines
beginning with '$ ' are valid comments.

However, there were many cases where lines in the message catalogs
contained just a single '$', without the required space after it.

Under linux, this caused 126766 error lines (in my builds) of the
form:

... unknown directive `': line ignored

This also causes gencat to exit with a non-0 exit code.  Even though
gencat says it ignores the line, it really doesn't.

An early porting change to programs/localized/util/merge.c was made to
ignore this return value on linux.  This hack has now been removed.

Build logs are a lot smaller and cleaner now.

cde/programs/dtscreen/dtscreen.msg

@@ -1,19 +1,19 @@
 $ $XConsortium: dtscreen.msg /main/5 1996/08/12 12:02:15 pascale $
 $ @(#)25	1.1.1.1  com/XTOP/aixclients/xlock/xlock.msg, xclients, r5gos325, 9333325d 5/6/93 20:13:37
-$
+$ 
 $ COMPONENT_NAME: dtscreen
-$
+$ 
 $ FUNCTIONS: dtscreen.msg
-$
-$
+$ 
+$ 
 $ (C) COPYRIGHT International Business Machines Corp. 1987, 1993
 $ All Rights Reserved
 $ Licensed Materials - Property of IBM
-$
+$ 
 $ US Government Users Restricted Rights - Use, duplication or
 $ disclosure restricted by GSA ADP Schedule Contract with IBM Corp.
-$
-$
+$ 
+$ 
 $ *                                                                      *
 $ * (c) Copyright 1993, 1994 Hewlett-Packard Company                     *
 $ * (c) Copyright 1993, 1994 International Business Machines Corp.       *