Fix various lint warnings in manuals

Fix "new sentence, new line" warnings throughout so that formatters
can produce correct spacing between sentences.

join.1
  Remove unnecessary Ns macros. These are not necessary for delimeters,
  which get special treatment.

xinstall.1
  Fix date in manual. The contents were last modified on 2016-12-03,
  so use that instead of the invalid date.

grep.1
  Fix escape sequence for `\<` and `\>`.

ed.1
  Remove spurious `\\n` escape for the null-command.

xinstall.1

@@ -1,4 +1,4 @@
-.Dd 2016-24-27
+.Dd 2016-12-03
 .Dt INSTALL 1
 .Os sbase
 .Sh NAME
@@ -31,7 +31,8 @@ If more than one
 .Ar source
 is given
 .Ar dest
-is treated as a directory. Otherwise
+is treated as a directory.
+Otherwise
 .Ar dest
 is treated as a filename.
 .Nm
@@ -52,12 +53,13 @@ Change the installed files' group to
 .Ar group .
 This may be a group name or a group identifier.
 .It Fl m Ar mode
-Change the file modes. Both numerical and symbolic
-values are supported. See
+Change the file modes.
+Both numerical and symbolic values are supported.
+See
 .Xr chmod 1
 for the syntex.
-Default mode 0755. If a file has the mode 0644 and
-is copied with
+Default mode 0755.
+If a file has the mode 0644 and is copied with
 .It Fl o Ar owner
 Change the installed files' owner to
 .Ar owner .
@@ -68,8 +70,8 @@ Copy files into the directory
 .Nm install ,
 the copy's mode will be 0755 unless
 .Fl m
-is used to select another mode. When the symbolic
-notation is used, the base mode is 0000.
+is used to select another mode.
+When the symbolic notation is used, the base mode is 0000.
 .El
 .Sh SEE ALSO
 .Xr chmod 1 ,
@@ -79,6 +81,6 @@ notation is used, the base mode is 0000.
 .Sh STANDARDS
 The
 .Nm
-utility is not standardized. This implementation is a subset
-of the GNU implementation and a subset with extensions to
-the FreeBSD implementation.
+utility is not standardized.
+This implementation is a subset of the GNU implementation and a subset
+with extensions to the FreeBSD implementation.