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/app-defaults/Dtwm.tmsg

@@ -35,12 +35,12 @@ $ *
 3 Two
 4 Three
 5 Four
-$
+$ 
 $ ----------------------------------------------------------------------------
 $ Do not translate message 6 - 10.
 $ These are not messages, but locale dependent values.
 $ ----------------------------------------------------------------------------
-$
+$ 
 $ VersionDialog_popup*columns = 40 for Single-byte
 $                               20 for Multi-byte
 6 40
@@ -80,12 +80,12 @@ $ * Dtwm*ws2*backdrop*image:
 14 SkyDark
 $ * Dtwm*ws3*backdrop*image: 
 15 Paver
-$
+$ 
 $ ----------------------------------------------------------------------------
 $ Do not translate message 17 - 20.
 $ These are not messages, but locale dependent values.
 $ ----------------------------------------------------------------------------
-$
+$ 
 $ Dtwm*FrontPanel*highResFontList
 17 -dt-interface system-medium-r-normal-m*-*-*-*-*-*-*-*-*:
 $ Dtwm*FrontPanel*mediumResFontList