xvidcore: fix build with gcc15

• add patch from fedora

Fixes build failure with gcc15:

In file included from ../../src/bitstream/bitstream.h:31,
                 from ../../src/decoder.c:40:
../../src/bitstream/../encoder.h:45:13: error: 'bool' cannot be defined via 'typedef'
   45 | typedef int bool;
      |             ^~~~
../../src/bitstream/../encoder.h:45:13: note: 'bool' is a keyword with '-std=c23' onwards
../../src/bitstream/../encoder.h:45:1: warning: useless type name in empty declaration
   45 | typedef int bool;
      | ^~~~~~~

xvidcore: cleanup

• replace rec with finalAttrs
• remove with lib; from meta
• replace sha256 with hash
  nix hash to-sri --type sha256 "1xyg3amgg27zf7188kss7y248s0xhh1vv8rrk0j9bcsd5nasxsmf"
  sha256-ruqulS1Ns5UkmDmjvQOEHWhEhD9aT4TCcf+I96oaz/c=

Tested build with:

nix-build --expr 'with import ./. {}; xvidcore.override { stdenv = gcc15Stdenv; }'

Part of fixes for gcc15 update:
#440456

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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