xz man page: Change \- (minus) to \(en (en-dash) for a numeric range.

Docs of ancient troff/nroff mention \(em (em-dash) but not \(en
and \- was used for both minus and en-dash. I don't know how
portable \(en is nowadays but it can be changed back if someone
complains. At least GNU groff and OpenBSD's mandoc support it.

Thanks to Bjarni Ingi Gislason for the patch.

src/xz/xz.1

@@ -840,7 +840,7 @@ The default
 .I size
 is three times the LZMA2 dictionary size or 1 MiB,
 whichever is more.
-Typically a good value is 2\-4 times
+Typically a good value is 2\(en4 times
 the size of the LZMA2 dictionary or at least 1 MiB.
 Using
 .I size
@@ -1325,7 +1325,7 @@ The default depends on the
 .IR preset :
 0 uses
 .BR hc3 ,
-1\-3
+1\(en3
 use
 .BR hc4 ,
 and the rest use
@@ -1441,11 +1441,11 @@ The default is
 .B fast
 for
 .I presets
-0\-3 and
+0\(en3 and
 .B normal
 for
 .I presets
-4\-9.
+4\(en9.
 .IP ""
 Usually
 .B fast
@@ -1464,7 +1464,7 @@ bytes is found, the algorithm stops
 looking for possibly better matches.
 .IP ""
 .I Nice
-can be 2\-273 bytes.
+can be 2\(en273 bytes.
 Higher values tend to give better compression ratio
 at the expense of speed.
 The default depends on the
@@ -1482,7 +1482,7 @@ and
 .IP ""
 Reasonable
 .I depth
-for Hash Chains is 4\-100 and 16\-1000 for Binary Trees.
+for Hash Chains is 4\(en100 and 16\(en1000 for Binary Trees.
 Using very high values for
 .I depth
 can make the encoder extremely slow with some files.
@@ -1523,7 +1523,7 @@ A BCJ filter converts relative addresses in
 the machine code to their absolute counterparts.
 This doesn't change the size of the data,
 but it increases redundancy,
-which can help LZMA2 to produce 0\-15\ % smaller
+which can help LZMA2 to produce 0\(en15\ % smaller
 .B .xz
 file.
 The BCJ filters are always reversible,
@@ -1642,7 +1642,7 @@ Specify the
 .I distance
 of the delta calculation in bytes.
 .I distance
-must be 1\-256.
+must be 1\(en256.
 The default is 1.
 .IP ""
 For example, with