curl_version_info.3: call the argument 'age'

Reported-by: Pete Lomax
Bug: https://curl.haxx.se/mail/lib-2017-12/0074.html

docs/libcurl/curl_version_info.3

@@ -26,11 +26,11 @@ curl_version_info - returns run-time libcurl version info
 .SH SYNOPSIS
 .B #include <curl/curl.h>
 .sp
-.BI "curl_version_info_data *curl_version_info( CURLversion "type ");"
+.BI "curl_version_info_data *curl_version_info( CURLversion "age ");"
 .ad
 .SH DESCRIPTION
 Returns a pointer to a filled in static struct with information about various
-features in the running version of libcurl. \fItype\fP should be set to the
+features in the running version of libcurl. \fIage\fP should be set to the
 version of this functionality by the time you write your program. This way,
 libcurl will always return a proper struct that your program understands,
 while programs in the future might get a different