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/localized/fr_FR.ISO8859-1/msg/dtmailopts.msg

@@ -179,14 +179,14 @@ $ ** You can edit this comment and add comments below each message.
 
 91 " "
 
-$
+$ 
 $	Used to construct the label on the "Printing" menu button in the
 $	"Category" option menu in the "Mailer - Options" dialog.
 $	This menu button is used to select printing options pane.
 $	This message is in the same menu as messages 4 - 10 above.
 92 "Impression"
 
-$
+$ 
 $	Used to construct the label on the "Mail Retrieval" menu button in the
 $	"Category" option menu in the "Mailer - Options" dialog.
 $	This menu button is used to select printing options pane.
@@ -194,7 +194,7 @@ $	This message is in the same menu as messages 4 - 10 above.
 $ "NEW-"
 93 "Mail Retrieval"
 
-$
+$ 
 $	Used to construct the label on the confirm attachment in the
 $	compose pane.
 $ "NEW-"