int http_setUserAgent(const char *newAgent);
Calling http_setUserAgent will change the default User Agent to newAgent for subsequent requests (until the next call to http_setUserAgent).
If you pass in NULL as an argument, HTTP Fetcher will NOT give the server a User Agent.
This function is useful for mimicing a browser, deceiving the webserver,
or a number of other creative uses.
On error, -1 is returned, and the previous value of
userAgent is unchanged. http_perror can be used to print an informative error message. http_strerror can be used to get a pointer to the current error description message.