Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Remove the const qualifier from iconv(3) to comply with POSIX:
http://pubs.opengroup.org/onlinepubs/9699919799/functions/iconv.html

Adjust all code that calls iconv.

PR: 199099
Exp-run by: antoine
MFC after: 2 weeks

- In the libiconv module for ISO 2022 restore the original order of the
fields of a private struct such that variables of this type are
initialised correctly. Fixes conversion from ISO 2022.
Also do this in the BIG5 module to prevent similar errors in the future.
- In the libiconv module for EUC-TW replace 2^cs with 1<<cs. Fixes
conversion from EUC-TW.
- Synchronise iconv code with NetBSD. In most cases this only updates
the RCS id because the changes are already there or are NetBSD specific.
+ libc/iconv/citrus_csmapper.c: Add a comment.
+ libc/iconv/citrus_db_factory.c: Remove put16().
+ libc/iconv/citrus_iconv.c: Return EINVAL on error.
+ libc/iconv/citrus_mapper.c: Return EINVAL on error.
+ libc/iconv/citrus_memstream.c: Fix type of a variable.
+ libc/iconv/citrus_prop.h: Sync definition of _CITRUS_PROP_HINT_END.
+ libc/iconv/citrus_stdenc.c: Return EINVAL on error.
+ libiconv_modules/mapper_std/citrus_mapper_std.c: Plug memory leak.

Obtained from: NetBSD
MFC after: 2 weeks

As a followup to r252547, propate const down the call stack.

Add the BSD-licensed Citrus iconv to the base system with default off
setting. It can be built by setting the WITH_ICONV knob. While this
knob is unset, the library part, the binaries, the header file and
the metadata files will not be built or installed so it makes no impact
on the system if left turned off.

This work is based on the iconv implementation in NetBSD but a great
number of improvements and feature additions have been included:

- Some utilities have been added. There is a conversion table generator,
which can compare conversion tables to reference data generated by
GNU libiconv. This helps ensuring conversion compatibility.
- UTF-16 surrogate support and some endianness issues have been fixed.
- The rather chaotic Makefiles to build metadata have been refactored
and cleaned up, now it is easy to read and it is also easier to add
support for new encodings.
- A bunch of new encodings and encoding aliases have been added.
- Support for 1->2, 1->3 and 1->4 mappings, which is needed for
transliterating with flying accents as GNU does, like "u.
- Lots of warnings have been fixed, the major part of the code is
now WARNS=6 clean.
- New section 1 and section 5 manual pages have been added.
- Some GNU-specific calls have been implemented:
iconvlist(), iconvctl(), iconv_canonicalize(), iconv_open_into()
- Support for GNU's //IGNORE suffix has been added.
- The "-" argument for stdin is now recognized in iconv(1) as per POSIX.
- The Big5 conversion module has been fixed.
- The iconv.h header files is supposed to be compatible with the
GNU version, i.e. sources should build with base iconv.h and
GNU libiconv. It also includes a macro magic to deal with the
char ** and const char ** incompatibility.
- GNU compatibility: "" or "char" means the current local
encoding in use
- Various cleanups and style(9) fixes.

Approved by: delphij (mentor)
Obtained from: The NetBSD Project
Sponsored by: Google Summer of Code 2009