Sync with OpenBSD.

  bc.y: Rev 1.50
  - write parse errors to stderr, prompted by Martijn Dekker
  - we're only interactive if stdout en stderr are a tty as well as stdin

PR:		234430
Obtained from:	OpenBSD

r313659:
Remove space at and of line

Reported by:	make manlint
MFC after:	2 days

r313660:
Remove empty Li

Reported by:	make manlint
MFC after:	2 days

r313661:
Escape Ss to avoid confusion by mdoc parser with the Ss macro

Reported by:	make manlint
MFC after:	2 days

r313662:
Add missing -width after -Bl -tag

Reported by:	make manlint
MFC after:	2 days

r313663:
Add missing section after .Xr reference

r313664:
Escape No to avoid confusion with the No macro

r313665:
Remove useless .Pp after the .Sh macro and remove empty line

r313666:
Remove empty space at EOL and escept Ed

r313667:
Remove spaces at EOL and sort correctly the SEE ALSO section

r313668:
Add missing section in manpage reference

r313669:
Properly use .An macro before Authors name

r313670:
Escape Sm to avoid confusion with Sm macro

r313671:
Use correct date format

r313672:
Remove useless Li macro

r313673:
Remove spaces at end of line

Reported by:	make manlint

These are no longer needed after the recent 'beforebuild: depend' changes
and hooking DIRDEPS_BUILD into a subset of FAST_DEPEND which supports
skipping 'make depend'.

Sponsored by:	EMC / Isilon Storage Division

Fix crashes and hangs found by AFL.
Improve handling of non-ascii chars.

Obtained from:	OpenBSD (CVS rev 1.49)

tty.c Rev. 1.3
Avoid unintended problems with operator precedence when doing an
assignment and comparison.

bc.1, Rev. 1.31, 1.32
'.Ql Quit' -> '.Ql quit' because only the lowercase command is valid.
Clarify sentence about `quit` in BUGS section.

extern.h, Rev. 1.12
whitespace

bc.y, Rev. 1.47
Prefer setvbuf() to setlinebuf() for portability

Obtained from:	OpenBSD
MFC after:	2 weeks

Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.

Still need to add real targets under targets/ to build packages.

Differential Revision:       D2796
Reviewed by: brooks imp

Reduce overlinking