The ROOT script samplehists.C creates three test files

- basic_lz4.root with 5 typical histograms, one of each data type
  - compressed with the default LZ4 compression
- advanced_zlib.root with two cycles of the same histogram
  - variable bin borders
  - compressed with the old default ZLIB compression
- broken_basic.root the same as basic_lz4.root but only the first 3kBytes
  - test ability to read broken files
