HLS input improvements:

- Added isOpen flag to the SegmentDownloader, so that we do not parse the data remaining from parseStreamHeader
- In inputHLS::firstSegment, use streamIsLive to determine vod vs live, rather than the size of userSelect
- Replaced check against 'smaller than zero', which always fails due to overflow of unsigned int
- Added print before downloading main playlist

src/input/input_hls.h

@@ -52,6 +52,7 @@ namespace Mist{
     size_t encOffset;
     unsigned char tmpIvec[16];
     mbedtls_aes_context aes;
+    bool isOpen;
   };
 
   class Playlist{