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/ja_JP.dt-eucJP/msg/dthello.msg

@@ -61,7 +61,7 @@ $    DO NOT TRANSLATE THESE MESSAGES
 
 $ Messages 4 and 5 are both used when there is a syntax error on
 $ the command line invoking dthello
-$
+$ 
 4 使用方法: %s [-display <ディスプレイ>] [-fg <フォアグラウンド・カラー>] [-bg <バックグラウンド・カラー>]\\\n
 5 [-font <フォント>] [-string <メッセージ>] [-file <ファイル名>] [-timeout <秒数>]\n