Fix T89976: Mirror Keys By Value performs wrong scale conversion

In the graph editor, Mirror Keys by Value would convert the value to mirror
over, to account for different units for linear & rotational properties.
The conversion was done in the different direction, though, resulting in
values that were too large by a factor of (180/pi)^2.

Deps builder: OIIO/OSL/ISPC/OIDN/LLVM/Flex updates

This diff somewhat snowballed out of updating OIDN to 1.4.1 it had some
changes that allowed us to remove the arm hacks we had in place and
revert to using identical versions for a whole bunch of deps. But that
required an update to ISPC which needed a newer LLVM and if we're
updating LLVM we may as well update OSL, and when we update OSL, OIIO
may as well be dragged in soo......anyhow...

This diff updates:

LLVM 9.0.0 (11.0.1 for mac/arm) -> 12.0.0
OIIO 2.1.15.0 -> 2.2.15.1
OSL 1.11.10.0 -> 1.11.14.1
winflex_bison 2.5.5-> 2.5.24 (ispc needed newer bison, windows only dep)
OIDN 1.4.0 -> 1.4.1
ISPC v1.14.1(random hash for mac/arm) -> v1.16.0
Flex 2.6.4 (ISPC needed newer Flex than available on CentOS 7)

and removes most of the "special arm/mac" versions. I think just ssl and
embree are left with special versions.

notable changes:
@LazyDodo included some clang headers in the linux/mac harvest which are
needed to start writing custom clang based tooling like D9465 these were
already shipping on windows, but not the other platforms.

[macOS] Change the `LC_ID_DYLIB` of OpenMP for {D11997}. This changes
where the executables look for dylibs.

Reviewed By: sebbas, LazyDodo

Differential Revision: https://developer.blender.org/D11748

Add `StringRef::trim()` functions

Add three functions that trim characters from the front & end of a
`StringRef`. All functions return a new `StringRef` that references a
sub-string of the original `StringRef`.

- `trim(chars_to_remove)`: strips all characters from the start and end
that occur in `chars_to_remove`.
- `trim(char_to_remove)`: same, but with a single character to remove.
- `trim()`: remove leading & trailing whitespace, so same as
`trim(" rnt")`

Reviewed By: JacquesLucke

Differential Revision: https://developer.blender.org/D12031

Deps: ensure osl/bin/oslc is using static libpng

Pass `-DLINKSTATIC=ON` to the OSL CMake, to ensure it statically links to
our libpng. Previously this was only applied on Windows, it's now on all
platforms.

Revert "GHOST/wayland: use Wayland only when 'BLENDER_WAYLAND' is set"

This reverts commit c971c851d38ad52779fa5d75c86bbfb83abf660b.

This change was part of the still-under-review patch D11489, which
hasn't been accepted yet.

Revert "cmake: enable Wayland by default"

This reverts commit a2ccd0e495d54240f785ee425a15ba1bd2537e5a.

This change was part of the still-under-review patch D11489, which
hasn't been accepted yet.

Bump subversion to avoid infinite enabling pose_library add-on

Bump Blender's sub-version to make sure the pose_library add-on isn't
auto-enabled on every run of Blender.

Versioning: move "until next subveresion bump" code

Move "until next subveresion bump" code into the 300.13 version block.
This should have happened in rB8d5b9478a25.

Pose backup: convert from C to C++

Convert `pose_backup.c` (in C) to `pose_backup.cc` (in C++). This will
make future improvements easier. For now, it's the same code with just
some additional explicit casts (C++ doesn't allow implicitly casting
`void *`), `NULL` changed into `nullptr`, and some other simple changes.

No functional changes.

Cleanup: fix clang-tidy warning modernize-use-nullptr

No functional changes.