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/app-defaults/Dtmail.tmsg

@@ -422,7 +422,7 @@ $ Message 101 mnenonic for 'Delete message'
 101 "Control<Key>D"
 $    
 $ ****************************************************************************   
-$
+$ 
 $ Message 102 mnenonic for 'Clear'
 102 e
 $ Message 103 and 104 are default window columns for Main window and Compose window. 
@@ -430,18 +430,18 @@ $ Multi byte locales should localized the column width to a smaller size.
 103 80
 104 80
 
-$
+$ 
 $ Messages 105 and 106 specify the fonts to be used in the renderTables
 $  for the printing output.  Message 105 is used by the headers and footers.
 $  Message 106 is used by the text portion.
-$
+$ 
 105 -dt-application-bold-r-normal-serif-0-120-0-0-m-0-*-*
 106 -dt-application-medium-r-normal-serif-0-100-0-0-m-0-*-*
 
-$
+$ 
 $ Message 107 is used to override the *Font resource place in the
 $  user's xrdb by xsession under CDE.
-$
+$ 
 $ "NEW-"
 107 -dt-application-medium-r-normal--*-120-75-75-p-74-dtsymbol-1