Description:
------------
While the method 'fetch' was called without the '$http_method' 
parameter.there while be an segmentfault.

REASON:

The *OAUTH_OVERRIDE_HTTP_METHOD* was added to the 
*oauth_fetch* function's parameter, so the pointer 
*final_http_method* was given the value of *method*(It is NULL 
while you dont pass the $http_method parameter)(l.1573).

Then the "strcmp"(l.1699) while trigger a segmentfault error.

Reproduce code:
---------------
...
2598     retcode = oauth_fetch(soo, fetchurl, http_method, request_args, request_headers, NULL, OAUTH_FETCH_USETOKEN | OAUTH_OVERRIDE_HTTP_METHOD TSRM     LS_CC);
...

...
1572     if(fetch_flags & OAUTH_OVERRIDE_HTTP_METHOD) {
1573         final_http_method = method;
...

...
1699         if (!strcmp(final_http_method, OAUTH_HTTP_METHOD_GET)) {
...


Expected result:
----------------
I think there maybe some way to gave the final_http_method a 
default value.