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/es_ES.ISO8859-1/msg/dtfile.msg

@@ -1283,7 +1283,7 @@ del Administrador de archivos abierta en el escritorio.  Si desea iniciar una nu
 del Administrador de archivos, deberá cerrar todas la ventanas del Administrador de archivos abiertas actualmente\n\
 y quitar todos los objetos del Administrador de archivos de las áreas de trabajo.
 
-$
+$ 
 $ "-NEW"
 40 "Could not connect to ToolTalk:\n%s\nExiting ..."