Implemented support for large streams in ZSTD compression

So far the limit was 16MB due to ROOT internal restrictions. This MR allows to use our own code for data sizes between 16MB and 2GB in order to deal with bigger events. It's backward compatible (oldl files can be read) but not forward compatible (old code cannot read new files). The reason is that large data use a different header for the internal stream with magic number 'ZS\2' instead of 'ZS\1'

Addresses Moore#349

Follow up developments in #177