Add AddressSanitizer support for clang-cl builds

Select the clang-cl-asan CMake preset (RelWithDebInfo, clang-cl,
ADDRESS_SANITIZER=ON) to instrument first-party code with AddressSanitizer.
The wiring lives in cmake/AddressSanitizer.cmake; SANITIZERS.md tells how to
add the clang-cl tools, build, and read the report.

Details:
- Add the clang-cl-asan preset so the asan build is one selection in Visual
  Studio, and a base for a CMakeUserPresets.json to inherit.
- Instrument first-party code only; the vendored libraries keep default flags.
- Use the release CRT and disable MSVC-STL container annotations, so
  instrumented and un-instrumented TUs stay compatible.
- Pass /bigobj to the TUs asan inflates past the COFF section cap.
- Link the asan runtime for clang-cl (lld-link does not infer it).
- Stub Bink into the exe: retail binkw32.dll cannot load in an asan process
  (its image base is the 32-bit shadow), so compile no-op exports instead.
- Route the asan report to gamedir/asan.report.<pid>, since every app is a
  WIN32 GUI app with no console to receive the default stderr report.
- Opt functions with 32-bit inline __asm out of instrumentation with
  cmake/asan-ignorelist.txt, one function at a time (asan reserves a register
  the asm needs). The rest of each translation unit stays instrumented.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SANITIZERS.md

@@ -0,0 +1,53 @@
+# AddressSanitizer
+
+AddressSanitizer (asan) finds memory errors at runtime: out-of-bounds accesses,
+use-after-free, and similar. It reports the exact faulting access.
+
+## Requirements
+
+asan requires `C++ Clang tools for Windows` (MSVC's AddressSanitizer does not
+support -fsanitize-ignorelist).
+
+It is NOT installed by default . You can install it via the Visual Studio
+Installer.
+
+## Build and run
+
+Either use the included `clang-cl-asan` preset, or inherit from it in your own
+`CMakeUserPresets.json`
+
+## Debug from Visual Studio
+
+asan needs `clang_rt.asan_dynamic-i386.dll` at run time. MSVC ships this DLL
+with the x86 tools, but Visual Studio does not add that folder to the debugger
+PATH. To start the exe with F5, add the tools folder to the
+debugger PATH:
+
+1. Access the CMake Targets View in Solution Explorer
+2. Right-click the exe target (for example `JA2.exe`) and select `Add Debug Configuration`. 
+   Visual Studio creates `launch.vs.json` in the `.vs` folder and adds a configuration with
+   the correct `projectTarget`.
+3. Add an `env` block to that configuration:
+
+```json
+      "env": {
+        "PATH": "C:\\Program Files\\Microsoft Visual Studio\\18\\Community\\VC\\Tools\\MSVC\\14.51.36231\\bin\\Hostx64\\x86;${env.PATH}"
+      }
+```
+
+Set the first path to the `bin\Hostx64\x86` folder of your MSVC tools. To find
+it, search your Visual Studio installation for `clang_rt.asan_dynamic-i386.dll`.
+Your edition (`Community`), MSVC version (`14.51.36231`), and host (`Hostx64` or
+`Hostx86`) can differ.
+
+## Reading the report
+
+Every app is a GUI app with no console, so asan writes the report to a file by
+default:
+
+```
+gamedir/asan.report.<pid>
+```
+
+When asan finds an error, the run stops and the report names the faulting access.
+Set the `ASAN_OPTIONS` environment variable to change asan behaviour.