Curl move header list into read state to support double state
Fix: now mp4 file on internet url can be played by dvdplayer by double session support of cache.
Also apply double cache for avi files.
When using double cache, do not increase the total memory cost.
Merge pull request #2229 from ulion/file_double_cache

Fix: now mp4 file on internet url can be played by dvdplayer by double session support of cache.