cli.c: usage with argv[0]

Instead of printing a usage message with the "numericx" string as a
program name, uses argv[0], better for debugging log readability.

Signed-off-by: Daniel Santos <dacs.git@brilhante.top>

cli.c

@@ -111,7 +111,7 @@ main(int argc, char* argv[])
 	/* argument processing */
 	if( !(argc == 2) )
 	{
-		fprintf(stderr, "usage: %s <number>\n", "numericx");
+		fprintf(stderr, "usage: %s <number>\n", argv[0]);
 		return E2BIG;
 	}