Added lz4 and zstd comporessions to squashfs.

Newest squashfs in upstream has supported LZ4 (5) and ZSTD
(6) as compression algorithms. However, they didn't exist in binwalk's
current magic library. This commit added the magic values so that squashfs images
compressed by these algorithms could be successfully identified.

Ref:
https://github.com/torvalds/linux/blob/master/fs/squashfs/squashfs_fs.h
https://github.com/file/file/blob/master/magic/Magdir/filesystems

src/binwalk/magic/filesystems

@@ -216,8 +216,10 @@
 >>20    beshort 2       \blzma,
 >>20    beshort 3       \bgzip (non-standard type definition),
 >>20    beshort 4       \bxz,
+>>20    beshort 5       \blz4,
+>>20    beshort 6       \bzstd,
 >>20    beshort 0       \b{invalid},
->>20    beshort >4      \b{invalid},
+>>20    beshort >6      \b{invalid},
 >28     beshort <3
 >>8     belong  x       size: %d bytes,
 >>8     belong  x       \b{jump:%d}
@@ -256,8 +258,10 @@
 >>20    leshort 2       \blzma,
 >>20    leshort 3       \bgzip (non-standard type definition),
 >>20    leshort 4       \bxz,
+>>20    leshort 5       \blz4,
+>>20    leshort 6       \bzstd,
 >>20    leshort 0       \b{invalid},
->>20    leshort >4      \b{invalid},
+>>20    leshort >6      \b{invalid},
 >28     leshort <3
 >>8     lelong  x       size: %d bytes,
 >>8     lelong  x       {size:%d}
@@ -299,8 +303,10 @@
 >>20    beshort 2       \blzma,
 >>20    beshort 3       \bgzip (non-standard type definition),
 >>20    beshort 4       \blzma (non-standard type definition),
+>>20    beshort 5       \blz4,
+>>20    beshort 6       \bzstd,
 >>20    beshort 0       \b{invalid},
->>20    beshort >4      \b{invalid},
+>>20    beshort >6      \b{invalid},
 >28     beshort <3
 >>8     belong  x       size: %d bytes,
 >>8     belong  x       {size:%d}
@@ -342,8 +348,10 @@
 >>20    beshort 2       \blzma,
 >>20    beshort 3       \bgzip (non-standard type definition),
 >>20    beshort 4       \bxz,
+>>20    beshort 5       \blz4,
+>>20    beshort 6       \bzstd,
 >>20    beshort 0       \b{invalid},
->>20    beshort >4      \b{invalid},
+>>20    beshort >6      \b{invalid},
 >28     beshort <3
 >>8     belong  x       size: %d bytes,
 >>8     belong  x       {size:%d}
@@ -386,8 +394,10 @@
 >>20    beshort 2       \blzma,
 >>20    beshort 3       \bgzip (non-standard type definition),
 >>20    beshort 4       \bxz,
+>>20    beshort 5       \blz4,
+>>20    beshort 6       \bzstd,
 >>20    beshort 0       \b{invalid},
->>20    beshort >4      \b{invalid},
+>>20    beshort >6      \b{invalid},
 >28     beshort <3
 >>8     belong  x       size: %d bytes,
 >>8     belong  <1      {invalid}
@@ -432,8 +442,10 @@
 >>20    leshort 2       \blzma,
 >>20    leshort 3       \bgzip (non-standard type definition),
 >>20    leshort 4       \bxz,
+>>20    leshort 5       \blz4,
+>>20    leshort 6       \bzstd,
 >>20    leshort 0       \b{invalid},
->>20    leshort >4      \b{invalid},
+>>20    leshort >6      \b{invalid},
 >28     leshort <3
 >>8     lelong  x       size: %d bytes,
 >>8     lelong  x       {size:%d}
@@ -475,8 +487,10 @@
 >>20    leshort 2       \blzma,
 >>20    leshort 3       \bgzip (non-standard type definition),
 >>20    leshort 4       \bxz,
+>>20    leshort 5       \blz4,
+>>20    leshort 6       \bzstd,
 >>20    leshort 0       \b{invalid},
->>20    leshort >4      \b{invalid},
+>>20    leshort >6      \b{invalid},
 >28     leshort <3
 >>8     lelong  x       size: %d bytes,
 >>8     lelong  x       {size:%d}