Denote multiple arguments with 'arg ...' not 'args'

A few programs used the plural in their synopsis which doesn't read as
clear as the obvious triple-dot notation.

mdoc(7) .Ar defaults to "file ..." if no arguments are given and consistent
use of 'arg ...' matches that behaviour.

Cleanup a few markups of the same argument so the text keeps reading
naturally;  omit unhelpful parts like 'if optional arguments are given,
they are passed along' for tools like time(1) and timeout(1) that obviously
execute commands with whatever arguments where given -- just like doas(1)
which doesn't mention arguments in its DESCRIPTION in the first place.

For expr(1) the difference between 'expressions' and 'expression ...' is
crucial, as arguments must be passed as individual words.

Feedback millert jmc schwarze deraadt
OK jmc

tmux.1

@@ -961,7 +961,7 @@ Will run
 directly without invoking the shell.
 .Pp
 .Ar command
-.Op Ar arguments
+.Op Ar argument ...
 refers to a
 .Nm
 command, either passed with the command and arguments separately, for example:
@@ -1538,8 +1538,7 @@ show debugging information about jobs and terminals.
 .Tg source
 .It Xo Ic source-file
 .Op Fl Fnqv
-.Ar path
-.Ar ...
+.Ar path ...
 .Xc
 .D1 Pq alias: Ic source
 Execute commands from one or more files specified by
@@ -3120,7 +3119,7 @@ Commands related to key bindings are as follows:
 .Op Fl nr
 .Op Fl N Ar note
 .Op Fl T Ar key-table
-.Ar key command Op Ar arguments
+.Ar key command Op Ar argument ...
 .Xc
 .D1 Pq alias: Ic bind
 Bind key
@@ -3216,7 +3215,7 @@ lists the command for keys that do not have a note rather than skipping them.
 .Op Fl c Ar target-client
 .Op Fl N Ar repeat-count
 .Op Fl t Ar target-pane
-.Ar key Ar ...
+.Ar key ...
 .Xc
 .D1 Pq alias: Ic send
 Send a key or keys to a window or client.
@@ -5821,8 +5820,7 @@ until it is dismissed.
 .Op Fl y Ar position
 .Ar name
 .Ar key
-.Ar command
-.Ar ...
+.Ar command Op Ar argument ...
 .Xc
 .D1 Pq alias: Ic menu
 Display a menu on