IntelliSense under clang-x64 doesn't support Microsoft integer suffixes

Environment

• OS and Version: Windows 10 Enterprise LTSC 21H2 (10.0.19044.3570)
• VS Code Version: 1.83.1
• C/C++ Extension Version: 1.17.5
• LLVM Version: 17.0.2

Bug Summary and Steps to Reproduce

Bug Summary:
When using IntelliSense mode clang-x64, IntelliSense doesn't recognize Microsoft integer suffixes (which are used in the Windows SDK), however it works when using IntelliSense mode msvc-x64. Despite that, these suffixes compile on Clang.

Steps to reproduce:

1. Create a main.c file containing:

int main(void) { return 0i32; }

or

// the Clang header has '#include_next <limits.h>' which includes limits.h
// from the Windows SDK, in turn using these integer suffixes
#include <limits.h>
int main(void) { return _I32_MAX; }

2. Set IntelliSense mode to clang-x64 in c_cpp_properties.json
3. Hover over integer constant
4. See error squiggle "extra text after expected end of number"
5. Compile using this command line: clang main.c -Weverything -o main.exe
6. No warnings or errors generated

Expected behavior:
Shouldn't display any error, or perhaps an error about compiler portability that explicitly states it's a Microsoft extension.

Configuration and Logs

c_cpp_properties.json:

{
    "configurations": [
        {
            "name": "Win32",
            "compilerPath": "C:/Program Files/LLVM/bin/clang.exe",
            "intelliSenseMode": "clang-x64",
            "configurationProvider": "ms-vscode.cpptools"
        }
    ],
    "version": 4
}

Logs:

-------- Diagnostics - 10/25/2023, 3:26:01 PM
Version: 1.17.5
Current Configuration:
{
    "name": "Win32",
    "compilerPath": "C:/Program Files/LLVM/bin/clang.exe",
    "intelliSenseMode": "clang-x64",
    "configurationProvider": "ms-vscode.cpptools",
    "compilerPathIsExplicit": true,
    "cStandardIsExplicit": false,
    "cppStandardIsExplicit": false,
    "intelliSenseModeIsExplicit": true,
    "compilerPathInCppPropertiesJson": "C:/Program Files/LLVM/bin/clang.exe",
    "configurationProviderInCppPropertiesJson": "ms-vscode.cpptools",
    "mergeConfigurations": false,
    "browse": {
        "path": [
            "${workspaceFolder}"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
cpptools version (native): 1.17.5.0
Translation Unit Mappings:
[ E:\vscode-cpptools bug\main.c ]:
    E:\vscode-cpptools bug\main.c
Translation Unit Configurations:
[ E:\vscode-cpptools bug\main.c ]:
    Process ID: 1268
    Memory Usage: 54 MB
    Compiler Path: C:\Program Files\LLVM\bin\clang.exe
    Includes:
        C:\Program Files\LLVM\lib\clang\17\include
        C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.37.32820\include
        C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.37.32820\atlmfc\include
        C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt
        C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\shared
        C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\um
        C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\winrt
        C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\cppwinrt
    Standard Version: c17
    IntelliSense Mode: windows-clang-x64
    Other Flags:
        --clang
        --clang_version=170002
        --ms_compatibility
Total Memory Usage: 54 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 5486

Other Extensions

Same behavior when the only enabled extension is C/C++.

Additional context

Start by reproducing the diagnostic with the issue's main.c example and the clang-x64 settings in c_cpp_properties.json, then trace the IntelliSense parsing path for integer literals under Microsoft compatibility. Done means Microsoft integer suffixes produce no erroneous squiggle in clang-x64 while the provided clang command continues to compile cleanly; add or update a regression test if the relevant test location is found.