Detect Samsung TV user agent and preserve against cached IP to fix video...

.../x-mkv

This patch addresses the problem of Samsung TVs not handling video/x-matroska for .mkv files.
It does this by:
1) caching the user-agent of HTTP requests to xbmc against the IP address
2) creating a samsung_tv "quirk" value and table to map .mkv files to video/x-mkv
3) fetching the user agent from the cache when it is not present (such as in the "HEAD" request from Samsung TVs)
4) using the MIME type update from the Samsung quirk table to return mkv files as video/x-mkv