sed.1: must use capital 'I' to make address RE ignore case

While here, remove a doubled space added in the previous commit.
Ride the date bump of the previous commit.

document the escape sequences in REs and the substitute command

NB: gsed's "\cx" is not supported and hence not documented.

PR bin/59453

branches: 1.43.8;
Remove trailing whitespace.

Use the same options like m4 (-g turns on GNU, -G turns off GNU) Suggested
by uwe@

Add -G to support GNU extensions

Command file argument to -f is not optional.

Suppress space after -I and -i options in description too.
XXX: This should be documented explicitly.

Suppress space after -I and -i options.

fix second line of synopsis.

Sort options. Use Ss for non-standard headers. New sentence, new line.
Add missing Op.

add -u (unbuffered output) after GNU sed.

After 2 comes...

Merge our changes.

branches: 1.32.4;
- Reference tr(1) in `SEE ALSO' section;
- bump date.

From Bug Hunting.

Bump date for previous (PR #45981): the change ("c") command starts a
new cycle.

The change ("c") command should start a new cycle.

Apply one line patch I posted in PR #45981 and document this in the
manual page.

Improve previous change with better wording.

"i.e." -> "i.e.," - from Snader_LB on IRC

branches: 1.27.2; 1.27.20; 1.27.24;
Sort options. Uppercase GNU.

Add a -r flag that is an alias for -E, for compatibility with gnu sed.

branches: 1.25.22;
Clarify location of `}'. Requested by joerg. Bump date.

Sort options. From Kouichirou Hiratsuka in PR 26255 (slightly changed).

Bump Dd for previous.

Point people to re_format(7) instead of regex(3) for
RE description; from Greg A. Woods.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22365, verified by myself.

Quote bang.

.Nm does not need a dummy argument ("") before punctuation or
for correct formatting of the SYNOPSIS any longer.

Generate <>& symbolically. I'm avoiding .../dist/... directories for now.

tweak the description of the n function

Note that the `n' function does not restart the script.

Add a -E flag to ed(1) and sed(1) so that they can use extended
regular expressions instead of just basic regular expressions.

Uppercase and unquote section headers, punctuation nit.

Punctuation character are magic to -mdoc and can't be used directly
as macro arguments unless combined with \&.

.Nm in SYNOPSIS except first one should be followed by "".

WARNSify, fix .Nm usage, deprecate register, getopt returns -1 not EOF

Changed order of STANDARDS and HISTORY subheads to conform with
specification in mdoc(7).

Fix broken uses of Dd. Both the mdoc and mdoc.samples pages agree:
.Dd is supposed to be invoked like:
.Dd month day, year
e.g. ".Dd January 25, 1989", rather than:
.Dd "month day, year"
which is what these pages did.

add missing backslash; from David Brownlee in PR bin/3321.
also cleanup RCSids a bit.

RCS ID police

Make it clearer how to use alternate delimiters in context patterns.

Fix typo.

RCS id's

update from Diomidis Spinellis <dspin@leon.nrcps.ariadne-t.gr>

Add RCS indentifiers.

branches: 1.1.1;
added Berkeley sed with mods to use GNU regex