Corresponding source for the experimental MK4 Vulkan 4x binary

Base commit: 0671c473dca27bc1e736d309282ea499ec67a59d
Working-tree source changes are included, not merely a patch against upstream.
Includes the original MAME build scripts and bundled third-party sources/licenses.
Local compiler: MSYS2 UCRT64 GCC 16.2.0. Release64, -O3, C++20, static linkage.
Compiled shader is embedded in src/mame/williams/midzeus_vulkan_spv.h.

For a clean Windows build, install the standard MAME Windows/MSYS2 build tools.
See docs/source/initialsetup/compilingmame.rst for dependency and setup details.
In the UCRT64 shell, from this source directory:
    make -j8 REGENIE=1 NOWERROR=1
This builds the full modified MAME as mame.exe; rename/copy it as needed.
Alternatively build the smaller driver subset using:
    make -j8 REGENIE=1 NOWERROR=1 SUBTARGET=mk4 SOURCES=src/mame/williams/midzeus.cpp
The subset build is a convenience, not the exact full-driver distributed binary.

With the full release64 build tree already generated, the local incremental path:
    MK4_VK_TARGET=mame-vulkan-remaster.exe bash tools/mk4-vulkan/build.sh
This runs backend checks, links a separate executable and runs MAME validation.
To regenerate SPIR-V, install glslang and run:
    python tools/mk4-vulkan/compile_shader.py /path/to/glslang.exe
The compiler/SDK is not needed to use the pre-generated embedded shader.

A clean-room rebuild was not performed when making this archive. Build output
can differ by toolchain and timestamps; no bit-for-bit reproducibility claim.
All original copyright and license notices are retained.
