bashism
add min_buffer parameter.

For live streaming reducing min_buffer allows us to switch from a feed to another much faster.
merged from https://github.com/r0ro/HLSprovider/commit/59c6622cfd6b0740a7108e95f6ef1afe025e96cc
HLSProviderChromeless.swf:add a callback when video size is available, handle stage resize
merged from https://github.com/r0ro/HLSprovider/commit/ee27c367c54f191abb2b005af76818b7155f6199