+- .while and .shift
+ found by jca@ in ratpoison(1) Sun, 30 Jun 2013 12:01:09 +0200
+
+- \c (interrupted text) should prevent the line break
+ even inside .Bd literal; that occurs in chat(8)
+ also found in cclive(1) - DocBook output
+
+- \h horizontal move
+ found in cclive(1) DocBook output
+ Anthony J. Bentley on discuss@ Sat, 21 Sep 2013 22:29:34 -0600
+
+- \n+ and \n- numerical register increment and decrement
+ found by bentley@ in sbcl(1) Mon, 9 Dec 2013 18:36:57 -0700
+
+- \w'' width measurements
+ would not be very useful without an expression parser, see below
+ needed for Tcl_NewStringObj(3) via wiz@ Wed, 5 Mar 2014 22:27:43 +0100
+
+- using undefined strings or macros defines them to be empty
+ wl@ Mon, 14 Nov 2011 14:37:01 +0000
+
+- general expression parser, including arithmetics
+ to be used at least for .if/.ie and .nr and maybe at other places
+ could use J.T.Conklin's PD code in bin/expr/expr.c for inspiration
+ needed for Tcl_NewStringObj(3) via wiz@ Wed, 5 Mar 2014 22:27:43 +0100