Adds LZ4 support by default if LZ4 is available

Adds LZ4 support by default if LZ4 is available

Simple makefile change + quick typename change

Test:

  make clean
  make
  # successfully produces binary without lz4 support

  make clean
  # with flags to pick up my lz4 build
  make MOREFLAGS="-L/home/felixh/prog/lz4/lib -I/home/felixh/prog/lz4/lib"
  # successfully produces binary with lz4 support

  echo "TEST TEST TEST THIS IS A TEST STRING PLEASE TEST THIS PLEASE OK THANK YOU" | \
    ./lz4/lz4 | \
    LD_LIBRARY_PATH=/home/felixh/prog/lz4/lib ./zstd/zstd -d
  # successfully prints TEST TEST TEST THIS IS A TEST STRING PLEASE TEST THIS PLEASE OK THANK YOU