awful.client: Add a new section for layout related functions

The new stateful layout system try to avoid coupling and therefor
doesn't use these methods. It is not planned to deprecate the
stateless layout API, so these functions are just kept as-is with
the old naming convention.

lib/awful/client.lua

@@ -281,7 +281,7 @@ end
 
 --- Get the master window.
 --
--- @function awful.client.getmaster
+-- @legacylayout awful.client.getmaster
 -- @param[opt] s The screen number, defaults to focused screen.
 -- @return The master window.
 function client.getmaster(s)
@@ -291,7 +291,7 @@ end
 
 --- Set the client as master: put it at the beginning of other windows.
 --
--- @function awful.client.setmaster
+-- @legacylayout awful.client.setmaster
 -- @client c The window to set as master.
 function client.setmaster(c)
     local cls = util.table.reverse(capi.client.get(c.screen))
@@ -301,7 +301,7 @@ function client.setmaster(c)
 end
 
 --- Set the client as slave: put it at the end of other windows.
--- @function awful.client.setslave
+-- @legacylayout awful.client.setslave
 -- @client c The window to set as slave.
 function client.setslave(c)
     local cls = capi.client.get(c.screen)
@@ -724,6 +724,7 @@ end
 --- Calculate a client's column number, index in that column, and
 -- number of visible clients in this column.
 --
+-- @legacylayout awful.client.idx
 -- @client c the client
 -- @return col the column number
 -- @return idx index of the client in the column
@@ -784,6 +785,7 @@ end
 
 --- Set the window factor of a client
 --
+-- @legacylayout awful.client.setwfact
 -- @param wfact the window factor value
 -- @client c the client
 function client.setwfact(wfact, c)
@@ -836,6 +838,7 @@ end
 
 --- Increment a client's window factor
 --
+-- @legacylayout awful.client.incwfact
 -- @param add amount to increase the client's window
 -- @client c the client
 function client.incwfact(add, c)