Split tagging into a validation part including prioritization

in tag.{h,c} and {mdoc,man}_validate.c
and into a formatting part including command line argument checking
in term_tag.{h,c}, html.c, and {mdoc|man}_{term|html}.c.

Immediate functional benefits include:
* Improved prioritization of automatic tags for .Em and .Sy.
* Avoiding bogus automatic tags when .Em, .Fn, or .Sy are explicitly tagged.
* Explicit tagging of .Er and .Fl now works in HTML output.
* Automatic tagging of .IP and .TP now works in HTML output.
But mainly, this patch provides clean earth to build further improvements on.

Technical changes:
* Main program: Write a tag file for ASCII and UTF-8 output only.
* All formatters: There is no more need to delay writing the tags.
* mdoc(7)+man(7) formatters: No more need for elaborate syntax tree inspection.
* HTML formatter: If available, use the "string" attribute as the tag.
* HTML formatter: New function to write permalinks, to reduce code duplication.

Style cleanup in the vicinity while here:
* mdoc(7) terminal formatter: To set up bold font for children,
defer to termp_bold_pre() rather than calling term_fontpush() manually.
* mdoc(7) terminal formatter: Garbage collect some duplicate functions.
* mdoc(7) HTML formatter: Unify <code> handling, delete redundant functions.
* Where possible, use switch statements rather than if cascades.
* Get rid of some more Yoda notation.

The necessity for such changes was first discussed with kn@, but i didn't
bother him with a request to review the resulting -673/+782 line patch.

1 files changed, 5 insertions, 12 deletions

diff --git a/regress/regress.pl.1 b/regress/regress.pl.1
index 04a56912..73db6118 100644
--- a/regress/regress.pl.1
+++ b/regress/regress.pl.1
@@ -1,6 +1,6 @@
-.\"	$Id: regress.pl.1,v 1.4 2019/03/06 15:58:11 schwarze Exp $
+.\"	$Id: regress.pl.1,v 1.5 2020/03/13 15:32:31 schwarze Exp $
 .\"
-.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
+.\" Copyright (c) 2017, 2019, 2020 Ingo Schwarze <schwarze@openbsd.org>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above
@@ -14,7 +14,7 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: March 6 2019 $
+.Dd $Mdocdate: March 13 2020 $
 .Dt REGRESS.PL 1
 .Os
 .Sh NAME
@@ -78,6 +78,8 @@ output mode.
 Run subtests for
 .Fl T Cm markdown
 output mode.
+.It Cm tag
+Run subtests for automatic and manual tagging.
 .It Cm utf8
 Run subtests for
 .Fl T Cm utf8
@@ -146,15 +148,6 @@ subdirectory of the regression suite is not included.
 It uses a Makefile structure that differs vastly from the
 rest of the suite.
 .Sh BUGS
-On Oracle Solaris 11,
-.Xr diff 1
-does not support the
-.Fl a
-option.
-Delete that option from the following line in this script:
-.Pp
-.Dl my @diff = qw(diff -au);
-.Pp
 The C library function
 .Xr wcwidth 3
 is known to be buggy on Solaris, which may cause failures in the