[lua-library] Five oauth functions

* oauth_catenc
* oauth_get_nonce
* oauth_cmpstringp with qsort
* oauth_serialize_url
* oauth_sign_hmac_sha1

All those functions are being used in lua-flickr plugin already.
[grl-flickr-lua] Search & Browse Public & Personal

Using the oauth functions in lua-library of grilo this lua source
implements the same search and browse operation of the c flickr source.