Fix a regression that crept in in man_term.c 1.73 and mdoc_term.c 1.144.

Fix a regression that crept in in man_term.c 1.73 and mdoc_term.c 1.144.
When the title line uses special characters, mandoc will segfault.
Thus, first set up the character tables, then print the header,
as we always did.

Found in OpenBSD /usr/src/usr.sbin/bind/bin/check/named-checkconf.8.

While here, set p->tabwidth in terminal_man() for symmetry
with terminal_mdoc(), as suggested by millert@ (and already
committed to OpenBSD earlier).   Since 5 is the default, this
is not strictly required, but it is certainly clearer and more
robust.

"looks fine" kristaps@