add zcat symlink support, suggested by @wtarreau

added some test
also updated relevant doc

+ fixed a mistake in `lz4` symlink support :
  lz4 utility doesn't remove source files by default (like zstd, but unlike gzip).
  The symlink must behave the same.

tests/.gitignore

@@ -24,6 +24,8 @@ pool
 poolTests
 invalidDictionaries
 checkTag
+zcat
+zstdcat
 
 # Tmp test directory
 zstdtest
@@ -53,6 +55,7 @@ tmp*
 *.gz
 result
 out
+*.zstd
 
 # fuzzer
 afl

tests/playTests.sh

@@ -239,8 +239,18 @@ $ZSTD -c hello.tmp > hello.zstd --no-check
 $ZSTD -c world.tmp > world.zstd --no-check
 cat hello.zstd world.zstd > helloworld.zstd
 $ZSTD -dc helloworld.zstd > result.tmp
-cat result.tmp
 $DIFF helloworld.tmp result.tmp
+$ECHO "testing zstdcat symlink"
+ln -sf $ZSTD zstdcat
+./zstdcat helloworld.zstd > result.tmp
+$DIFF helloworld.tmp result.tmp
+rm zstdcat
+rm result.tmp
+$ECHO "testing zcat symlink"
+ln -sf $ZSTD zcat
+./zcat helloworld.zstd > result.tmp
+$DIFF helloworld.tmp result.tmp
+rm zcat
 rm ./*.tmp ./*.zstd
 $ECHO "frame concatenation tests completed"