Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r251565:

Print file names without stdio buffering to avoid mixing buffered and
unbuffered ouput.

PR: bin/176886

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Remove the advertising clause from UCB copyrighted files in usr.bin. This
is in accordance with the information provided at
ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change

Also add $FreeBSD$ to a few files to keep svn happy.

Discussed with: imp, rwatson

Change the behaviour of -F slightly; it now persists (forever) in
trying to open files rather than giving up when it encounters an
error. ENOENT errors are not reported.

As a result, files that are moved away then recreated are not at
risk of being 'lost' to tail. Files that are recreated and
temporarily have unreadable permissions will be shown when they
are fixed.

This behaviour is consistent with the GNU version of tail but
without the verbiage that goes with the GNU version.

This change also fixes error messages accompanying -f and -F.
They no longer report problems with (null)!

MFC after: 3 weeks

Add a -q option to suppress header lines when multiple files are specified.

Approved by: cperciva (mentor)
MFC after: 1 week

Add support for following more than one file i.e.
tail -f file1 file2

remove __P

WARNS=2 fixes, use __FBSDID().

File positions are off_t nowdays, not long, so:
long -> off_t
strtol -> strtoll
fseek -> fseeko

NOTE: that fseek not works for >long offsets files per POSIX:

[EOVERFLOW] For fseek( ), the resulting file offset would be a value which
cannot be represented correctly in an object of type long.

Fix tail to work on files bigger than 2GB.

PR: 14786
Reviewed by: iedowse

Add a new -F flag which is a superset of -f. It will cause tail to
stat() the file being followed and do a close/reopen if the file has been
renamed and/or rotated. This is damn useful for leaving running on files
in /var/log when newsyslog(8) rotates them.

Argh! caught! *blush*.. This program was supplying it's own 'err' routine
which was slightly different to the libc one. To save any more cunfusion,
use the libc one.

when file can be opened for read but cannot be read from:
fail once (was twice) in forward case
fail once (was no times) in reverse case

this can happen when file is a directory on an NFS or procfs mount.

This commit was generated by cvs2svn to compensate for changes in r1590,
which included commits to RCS files with non-trunk default branches.

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