Mention first version with CURLOPT_COPYPOSTFIELDS.

Don't confuse NUL with NULL.

ares/ares_expand_string.3

@@ -28,7 +28,7 @@ ares_expand_string \- Expand a length encoded string
 .SH DESCRIPTION
 The
 .B ares_expand_string
-function converts a length encoded string to a NULL terminated C
+function converts a length encoded string to a NUL-terminated C
 string.  The argument
 .I encoded
 gives the beginning of the encoded string, and the arguments