bin/45164: mandoc(1) do not expand macros in sub-section definition

[njoly%pasteur.fr@localhost]

>Number:         45164
>Category:       bin
>Synopsis:       mandoc(1) do not expand macros in sub-section definition
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jul 21 18:00:00 +0000 2011
>Originator:     Nicolas Joly
>Release:        NetBSD 5.99.55
>Organization:
Institut Pasteur
>Environment:
System: NetBSD lanfeust.sis.pasteur.fr 5.99.55 NetBSD 5.99.55 (LANFEUST) #1: 
Thu Jul 21 13:18:13 CEST 2011 
njoly%lanfeust.sis.pasteur.fr@localhost:/local/src/NetBSD/obj.amd64/sys/arch/amd64/compile/LANFEUST
 amd64
Architecture: x86_64
Machine: amd64
>Description:
It seems that mandoc(1) does not expand macros in sub-section definition (Ss),
where nroff do.

By example, installboot(8) man page output is not nice.

njoly@lanfeust [~]> mandoc /usr/share/man/man8/installboot.8 | grep 'Nx'
   Nx Ns Tn /macppc files
   Nx Ns Tn /next68k files
   Nx Ns Tn /sparc64 files
   Nx Ns Tn /amiga
   Nx Ns Tn /ews4800mips
   Nx Ns Tn /i386 and Nx Ns Tn /amd64
   Nx Ns Tn /macppc
   Nx Ns Tn /next68k
   Nx Ns Tn /pmax
   Nx Ns Tn /sparc
   Nx Ns Tn /sparc64
   Nx Ns Tn /sun2 and Nx Ns Tn /sun3
   Nx Ns Tn /alpha
   Nx Ns Tn /hp300
   Nx Ns Tn /i386 and Nx Ns Tn /amd64
   Nx Ns Tn /macppc
   Nx Ns Tn /next68k
   Nx Ns Tn /pmax
   Nx Ns Tn /sun2 and Nx Ns Tn /sun3
   Nx Ns Tn /vax

>How-To-Repeat:
Check installboot(8) man page, formatted with mandoc.
>Fix: