xz: A couple of man page fixes.

Now the interaction of presets and custom filter chains
is described correctly. Earlier it contradicted itself.

Thanks to DevHC who reported these issues on IRC to me
on 2012-12-14.

src/xz/xz.1

@@ -5,7 +5,7 @@
 .\" This file has been put into the public domain.
 .\" You can do whatever you want with this file.
 .\"
-.TH XZ 1 "2012-10-03" "Tukaani" "XZ Utils"
+.TH XZ 1 "2013-06-21" "Tukaani" "XZ Utils"
 .
 .SH NAME
 xz, unxz, xzcat, lzma, unlzma, lzcat \- Compress or decompress .xz and .lzma files
@@ -897,11 +897,14 @@ if threading will be enabled by default.
 .SS "Custom compressor filter chains"
 A custom filter chain allows specifying
 the compression settings in detail instead of relying on
-the settings associated to the preset levels.
+the settings associated to the presets.
 When a custom filter chain is specified,
-the compression preset level options
-(\fB\-0\fR ... \fB\-9\fR and \fB\-\-extreme\fR) are
-silently ignored.
+preset options (\fB\-0\fR ... \fB\-9\fR and \fB\-\-extreme\fR)
+earlier on the command line are forgotten.
+If a preset option is specified
+after one or more custom filter chain options,
+the new preset takes effect and
+the custom filter chain options specified earlier are forgotten.
 .PP
 A filter chain is comparable to piping on the command line.
 When compressing, the uncompressed input goes to the first filter,
@@ -934,6 +937,15 @@ Extra commas in
 are ignored.
 Every option has a default value, so you need to
 specify only those you want to change.
+.PP
+To see the whole filter chain and
+.IR options ,
+use
+.B "xz \-vv"
+(that is, use
+.B \-\-verbose
+twice).
+This works also for viewing the filter chain options used by presets.
 .TP
 \fB\-\-lzma1\fR[\fB=\fIoptions\fR]
 .PD 0
@@ -976,13 +988,12 @@ The only supported modifier is currently
 .BR e ,
 which matches
 .BR \-\-extreme .
-The default
-.I preset
-is
-.BR 6 ,
-from which the default values for the rest of the LZMA1 or LZMA2
+If no
+.B preset
+is specified, the default values of LZMA1 or LZMA2
 .I options
-are taken.
+are taken from the preset
+.BR 6 .
 .TP
 .BI dict= size
 Dictionary (history buffer)
@@ -1578,7 +1589,7 @@ is supported only together with
 .BR \-\-info\-memory ,
 and
 .BR \-\-list .
-It will be supported for normal compression and
+It will be supported for compression and
 decompression in the future.
 .
 .SS Version