Add note about compressed files (SF #1536186)

docs/Changelog

@@ -35,6 +35,7 @@ pisg (0.69) - ??
      + Fix uninitialised values in charts (SF #1354920 and #1498999)
      + Fix Makefile to support the +CVS string and include it in releasename
      + Fix charts to not include "NULL" tracks. 
+     + Add note about compressed files (SF #1536186)
    * Features:
      + Add "+CVS" to versionstring and remove it in Makefile when running
        'make release'. This makes snapshot easier.

docs/pisg-doc.xml

@@ -434,7 +434,9 @@
     <para>
     <command>Format</command> is used to define the format of the logfile,
     pisg supports a various number of different logfiles, see the FORMATS
-    file included with the pisg distribution.
+    file included with the pisg distribution. If yourogfiles have the
+    suffix .gz or .bz2, they will automatically be decompressed and read by
+    pisg.
     See also <xref linkend="Maintainer" />.
     </para>
     </refsect1>