libogc Wiiuse IR math component port

Upstream: https://github.com/devkitPro/libogc
Pinned commit: a4064a86487c46d8ab76d4fdf99e8059a62c4fa2
Modified for switch-pico on 2026-09-11.

This directory is a source extraction from the Wiiuse component of libogc,
not an independent reimplementation and not a copy of ordinary Wiiuse from
another repository. Original sources in upstream/ are byte-for-byte copies
from the pin; UPSTREAM.json records their URLs, checksums and retained ranges.

LICENSE AND ATTRIBUTION

The full, unchanged wiiuse/license_libogc.txt from that libogc revision is
provided here as license_libogc.txt. It contains GNU GPL version 3 plus the
section 18 exception for linking with independent modules. The opening scope
restriction (libogc and its covered or combined works) is retained. This is a
modified port of that libogc component; we explicitly extend and retain the
section 18 linking exception for this version, including the portable header
and generated IR translation unit. This component is not offered under MIT.
The surrounding independent switch-pico project is not relicensed.

Section 18 permits linking this library with independent modules under their
own licenses and distributing the executable under terms of your choice,
provided each independent module's license is satisfied. An independent
module is not derived from or based on this library. The exception does not
remove the GPL obligations for this component itself, including provision of
its corresponding source when distributing it in object-code form. The
original component, extraction script and portable header are supplied in
source form. Recipients should retain these notices and the full license.

The original Wiiuse notice in upstream/wiiuse_internal.h credits Michael
Laforest, copyright 2006-2007, grants GPL version 3 or later, and disclaims
warranty. It is retained intact in that file, the portable header, and the
generated C. There is no copyright/license preamble in the pinned ir.c,
ir.h, definitions.h or gc/wiiuse/wiiuse.h; none has been invented for them.

The root libogc notice is preserved verbatim as libogc_license.txt. It credits
Michael Wiedenbauer (shagkur) and Dave Murphy (WinterMute), copyright 2004-2009,
and grants permission subject to origin, altered-source marking and notice
retention restrictions. This root notice does not replace the Wiiuse-specific
GPL plus exception. There is no root LICENSE file at the pinned revision;
UPSTREAM.json records the failed LICENSE URL and the actual pinned root file.

EXACT PORTABILITY CHANGES

1. Keep upstream/ir.c untouched. tools/prepare_libogc_ir.py selects the exact
   declared byte-preserving line ranges rather than rewriting any algorithm.
   No function body, algorithm constant, comparison, arithmetic expression or
   math-library call in the retained functions is changed.
2. Omit transport, report decoding, device setup and platform includes. No
   unused transport function is compiled, and no fake Wiiuse I/O implementation
   is supplied. The caller supplies decoded dots and orientation.
3. Supply a narrow C/C++ header instead of the Bluetooth/GEKKO headers. Keep
   the original ubyte, orient_t, ir_dot_t, fdot_t, sb_t, aspect_t, ir_position_t
   and ir_t declarations verbatim; supply the platform primitive f32 as float.
   Copy the original anonymous IR state enum and original aspect-size macros
   into this header. Add a unique include guard, C linkage and declarations
   for the two already-external functions find_sensorbar/apply_ir_smoothing.
   Retain the original calc_yaw/interpret_ir_data declarations.
4. Generated C starts with #include "libogc_ir/ir.h", includes standard math.h,
   and copies the original PI/angle conversion macros. The original disabled
   WIIUSE_DEBUG(fmt, ...) definition is retained, then redefined as
   WIIUSE_DEBUG(...) with the same empty expansion. This makes one-argument
   debug calls valid strict C11 without enabling logging, changing call sites,
   suppressing compiler warnings, or modifying algorithm bodies/constants.
5. Add dated modification/license comments, blank separators and #line
   directives around unchanged source sections. File names in those directives
   are repository-relative, so output is independent of the build directory.
   The extraction has no runtime dependency on Python or the filesystem.

The native relative-output adapter is separate from these upstream math
functions. It handles camera coordinate conventions, gravity units, camera
sequence consumption, configurable relative scale and USB delta baselines.
Those adaptations are not changes to the algorithm in this directory and do
not provide absolute host cursor synchronization.