Update zlib to 1.2.8
Add the 'rle' zstrategy
Fix testing with unicode paths

re needs unicode option
kernel: code_SUITE fix unicode option
Merge branch 'bjorn/erts/zlib-1.2.8'

* bjorn/erts/zlib-1.2.8:
  configure: Prefer the system's zlib over own our zlib source
  Update preloaded modules
  Add the 'rle' zstrategy
  Don't make gzio.c dependent on the zutil.h header file
  Update zlib to 1.2.8
  erts/zlib: Remove unused file example.c