Update INSTALL about the dependencies of the scripts.
diff --git a/INSTALL b/INSTALL
index d643693..ee32289 100644
--- a/INSTALL
+++ b/INSTALL
@@ -424,11 +424,16 @@
gl_cv_posix_shell=/path/to/posix-sh as an argument to the configure
script.
- Some of the scripts require also mktemp. The original mktemp can be
- found from <http://www.mktemp.org/>. On GNU, most will use the mktemp
- program from GNU coreutils instead of the original implementation.
- Both mktemp versions are fine for XZ Utils (and practically for
- everything else too).
+ xzdiff (xzcmp/lzdiff/lzcmp) may use mktemp if it is available. As
+ a fallback xzdiff will use mkdir to securely create a temporary
+ directory. Having mktemp available is still recommended since the
+ mkdir fallback method isn't as robust as mktemp is. The original
+ mktemp can be found from <http://www.mktemp.org/>. On GNU, most will
+ use the mktemp program from GNU coreutils instead of the original
+ implementation. Both mktemp versions are fine.
+
+ In addition to using xz to decompress .xz files, xzgrep and xzdiff
+ use gzip, bzip2, and lzop to support .gz, bz2, and .lzo files.
3.2. PATH
