cons: Add boot option to mute boot messages after banner

This is useful for embedded systems, where it provides feedback that the
kernel has booted, but avoids printing the probe messages. If both
mutemsgs and verbose are set, verbose cancels the mute.

Additionally, this unmutes the console on panic, so a user can see what
happened leading up to the panic.

Obtained from: Juniper Networks, Inc.

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

Revert "Revert "tslog: Annotate some early boot functions""

Now that <sys/tslog.h> is wrapped in #ifdef _KERNEL, it's safe to have
tslog annotations in files which might be built from userland (i.e. in
subr_boot.c, which is built as part of the boot loader).

This reverts commit 59588a546f55523d6fd37ab42eb08b719311d7d6.

Revert "tslog: Annotate some early boot functions"

The change to subr_boot.c broke the libsa build because the TSLOG
macros have their own definitions for the boot loader -- I didn't
realize that the loader code used subr_boot.c.

I'm currently testing a fix and I'll revert this revert once I'm
satisfied that everything works, but I don't want to leave the
tree broken for too long.

This reverts commit 469cfa3c30ee7a5ddeb597d0a8c3e7cac909b27a.

tslog: Annotate some early boot functions

Booting an amd64 kernel on Firecracker with 1 CPU and 128 MB of RAM,
hammer_time takes roughly 2740 us:
* 55 us in xen_pvh_parse_preload_data
* 20 us in boot_parse_cmdline_delim
* 20 us in boot_env_to_howto
* 15 us in identify_hypervisor
* 1320 us in link_elf_reloc
* 1310 us in relocate_file1 handling ef->rela
* 25 us in init_param1
* 30 us in dpcpu_init
* 355 us in initializecpu
* 255 us in initializecpu calling load_cr4
* 425 us in getmemsize
* 280 us in pmap_bootstrap
* 205 us in create_pagetables
* 10 us in init_param2
* 25 us in pci_early_quirks
* 60 us in cninit
* 90 us in kdb_init
* 105 us in msgbufinit
* 20 us in fpuinit
* 205 us elsewhere in hammer_time

Some of these are unavoidable (e.g. identify_hypervisor uses CPUID and
load_cr4 loads the CR4 register, both of which trap to the hypervisor)
but others may deserve attention.

Sponsored by: https://www.patreon.com/cperciva
Differential Revision: https://reviews.freebsd.org/D40325

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

boot: Remove stray free()

Early versions of this code had a free, but this one doesn't need
it. Remove the forgotten free(vv); from earlier versions.

Fixes: ed56dcfc6b1f
Noticed by: Michael Butler
Sponsored by: Netflix

boot: pass in args as const

Copy the arg that sets a variable to maximize the reuse of this
routine. There are places we call it from that are const char * and it
might not be safe to cast that away.

Sponsored by: Netflix

When parsing command line stuff, treat tabs and spaces the same.

When creating complex config files, people like to use tabs to offset
sections. Treat them the same as spaces for delimiters.

Regularize the Netflix copyright

Use recent best practices for Copyright form at the top of
the license:
1. Remove all the All Rights Reserved clauses on our stuff. Where we
piggybacked others, use a separate line to make things clear.
2. Use "Netflix, Inc." everywhere.
3. Use a single line for the copyright for grep friendliness.
4. Use date ranges in all places for our stuff.

Approved by: Netflix Legal (who gave me the form), adrian@ (pmc files)

Create helper functions for parsing boot args.

boot_parse_arg to parse a single arg
boot_parse_cmdline to parse a command line string
boot_parse_args to parse all the args in a vector
boot_howto_to_env Convert howto bits to env vars
boot_env_to_howto Return howto mask mased on what's set in the environment.

All these routines return an int that's the bitmask of the args
translated to RB_* flags. As a special case, the 'S' flag sets the
comconsole_speed env var. Any arg that looks like a=b will set the env
key 'a' to value 'b'. If =b is omitted, 'a' is set to '1'. This
should help us reduce the number of redundant copies of these routines
in the tree. It should also give a more uniform experience between
platforms.

Also, invent a new flag RB_PROBE that's set when 'P' is parsed. On
x86 + BIOS, this means 'probe for the keyboard, and if it's not there
set both RB_MULTIPLE and RB_SERIAL (which means show the output on
both video and serial consoles, but make serial primary). Others it
may be some similar concept of probing, but it's loader dependent
what, exactly, it means.

These routines are suitable for /boot/loader and/or the kernel,
though they may not be suitable for the tightly hand-rolled-for-space
environments like boot2.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D16205