Drop list.c, add new cmd_arg.c..
Move getmsglist() and other message related things from list.c to
message.c (XXX bad name!?), and getrawlist() and such from list.c
to new cmd_arg.c.
On the long run getmsglist() and the underlaying stuff will be
rewritten completely, at which time getmsglist() core will be
moved to cmd_arg.c itself.
Add a new function series to create command lists for
sh(1)ell-style quoted arguments.
TODO v15 will make this more generic so that cmd_tab.h in fact can
TODO use the new datatypes and all this is automatic in that it
TODO can be used by the lexer as such. Not yet.