curl.1: fix missing space in section --data

docs/curl.1

@@ -317,7 +317,7 @@ using the content-type application/x-www-form-urlencoded.  Compare to
 
 \fI-d, --data\fP is the same as \fI--data-ascii\fP. \fI--data-raw\fP is almost
 the same but does not have a special interpretation of the @ character. To
-post data purely binary, you should instead use the\fI--data-binary\fP option.
+post data purely binary, you should instead use the \fI--data-binary\fP option.
 To URL-encode the value of a form field you may use \fI--data-urlencode\fP.
 
 If any of these options is used more than once on the same command line, the