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/C/config/_common.session.tmsg

@@ -11,11 +11,11 @@ $ * (c) Copyright 1995 FUJITSU LIMITED.
 $ * (c) Copyright 1995 Hitachi.
 $ *
 $ * $XConsortium: _common.session.tmsg /main/1 1995/12/09 11:42:39 barstow $
-$
+$ 
 $ *****************************************************************************
-$
+$ 
 $set 1
-$
+$ 
 $ *****************************************************************************
 $ *
 $ *  The following message is used for the session name for a home