Separate global support for "extra attribute codes" from per sub-board support

Each sub-board now has its own separate set of toggles for extra attribute
code support (set in the pmode property of sub-boards) via new pmode flags:
P_WWIV, P_WILDCAT, P_PCBOARD, P_RENEGADE, and P_CELERITY

The P_NOXATTRS flag is no longer handled in putmsg() - has no effect.
P_NOXATTRS can be passed to printfile()/menu() however to override the
global set of extra attribute support flags.

The expansion of "pipe codes" is no longer auto-disabled when the user is
using a RIP terminal.

Global extra attribute support was moved from SCFG->Message Options to
SCFG->System, since the global option now have no effect on displaying
messages. The global setting is just the default set of extra attributes
supported for display files (e.g. menus).

wordwrap() now has a bit more simplified API (one less argument), though
supporting the old usage for JS word_wrap() backward compatibilty.

This addresses issue #892.