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/Dtcalc.tmsg

@@ -27,24 +27,24 @@ $ *****************************************************************************
 $set 1
 $ 
 $ Messages 1 & 2 are the default width and height of the calculator.
-$
+$ 
 1 375
 2 540
 $ 
 $ Messages 3 & 4 are the minimum width and height to the calculator.  These
 $ may need to change as label sizes change for different languages.
-$
+$ 
 3 375
 4 540
-$
+$ 
 $ Message 5 is the value for the resource Dtcalc*display.XmNcolumns:.  It's 
 $ defaultin non Multi-byte languages will be 1.  It controls the Display Area 
 $ text widget and the ASCII converter text widget.
-$
+$ 
 5 1
-$
+$ 
 $ Message 6 is the value for the resource Dtcalc*aframe*XmNcolumns:.  It's 
 $ defaultin non Multi-byte languages will be 1.  It controls the ASCII
 $ converter text widget.
-$
+$ 
 6 1