webkitgtk: upgrade 2.48.5 -> 2.50.0

webkitgtk: upgrade 2.48.5 -> 2.50.0

Dropped fix-armv7-compilation.patch, because it is included in this
release.
Dropped no-musttail-arm.patch, because it has been solved by project
(a bit differently)[1]

Added a new backported patch, fix-musl-compilation.patch
to avoid build error when compiling with musl libc:

.../Source/bmalloc/libpas/src/libpas/pas_probabilistic_guard_malloc_allocator.c:52:10: fatal error: execinfo.h: No such file or directory
|    52 | #include <execinfo.h>
|       |          ^~~~~~~~~~~~

Another patch, fix_op_instanceof_handler_for_32-bit_C-loop_build.patch is under review by
upstream. It fixes compiling for 32-bit targets by fixing the following error:

error: label 'op_instanceof_return_location' used but not defined

[1]: https://github.com/WebKit/WebKit/blob/webkitgtk-2.50.0/Source/WTF/wtf/Compiler.h#L280

Changelog:
2.50.0:
- Fix rendering with software rasterization enabled.
- Fix WebAudio issues after idling for a minute.
- Fix several crashes and rendering issues.

2.49.90:
- Add support for font collection / fragment identifiers.
- Fix web process deadlock on exit.
- Fix stuttering when playing WebP animations
- Fix CSS animations with cubic-bezier timing function.
- Do not start the MemoryPressureMonitor if it's disabled
- Translation updates: Polish, Slovenian.
- Fix several crashes and rendering issues.

2.49.4:
- Enable CSS property font-variant-emoji is now enabled by default.
- Improve emoji font selection.
- Add SVT-AV1 encoder support to media backend.
- Show device scale factor in webkit://gpu.
- Fix font rendering of composed characters with certain fonts.
- Fix handling of font synthesis properties (bold/italic).
- Fix documentation of WebKitDeviceInfoPermissionRequest.
- Fix several crashes and rendering issues.

2.49.3:
- Add new API to get the theme color of a WebKitWebView.
- Fix rendering with GTK 3.
- Notify automation session on abnormal disconnections.
- Fix a crash by ensuring SkiaRecordingResult is destroyed on the main thread.
- Fix build on s390x.
- Fix the build with GTK 3.
- Fix several crashes and rendering issues.

2.49.2:
- Enable damage propagation to the UI process by default.
- Pass available input devices from UI process to web process for Interaction Media Features.
- Always have a fallback when domain does not have known base.
- Fix URL after HSTS upgrade in case of redirection.
- Fix rendering when device scale factor change comes before the web view geometry update.
- Ensure web view is focused on tap gesture.
- Fix a crash when setting WEBKIT_SKIA_GPU_PAINTING_THREADS=0.
- Fix several crashes and rendering issues.
- Translation updates: Brazilian Portuguese, Swedish.

2.49.1:
- Change threaded rendering implementation to use Skia API instead of WebCore display
  list that is not thread safe. This also allowed to improve performance by recording
  layers once and replaying every dirty region in different worker threads.
- Added hybrid rendering mode that tries to use the GPU worker threads, but if they
  are all busy the CPU worker threads are used if possible.
- Add volume locking support to media player.
- Add support for tracing counters with Sysprof.
- Fix several crashes and rendering issues.

Signed-off-by: Gyorgy Sarvari <skandigraun@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>