请求增加clang-LLVM工具集支持

[hzqst]

当前版本VC_LTL不支持LLVM工具集编译，我做了一些修改让VC-LTL强行支持：

1.\VCLTL\config\config.props

<!--计算机已经安装LLVM-->
<VC-LTLUsedToolsVersion Condition=" ('$(VC-LTLUsedToolsVersion)'=='') And ('$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\LLVM\LLVM'!='') ">14.0.24231</VC-LTLUsedToolsVersion>
<VC-LTLUsedToolsVersion Condition=" ('$(VC-LTLUsedToolsVersion)'=='') And ('$(Registry:HKEY_LOCAL_MACHINE\SOFTWARE\LLVM\LLVM'!='') " >14.0.24231</VC-LTLUsedToolsVersion>

<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='v140')">true</SupportPlatformToolsetNormal>
<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='v141')">true</SupportPlatformToolsetNorma>

<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='LLVM-vs2015_xp')">true</SupportPlatformToolsetNormal>
<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='LLVM-vs2017_xp')">true</SupportPlatformToolsetNormal>

<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='LLVM-vs2015')">true</SupportPlatformToolsetNormal>
<SupportPlatformToolsetNormal Condition="('$(SupportPlatformToolsetNormal)'=='') And ('$(PlatformToolset)'=='LLVM-vs2017')">true</SupportPlatformToolsetNormal>

2.修改\VCLTL_msvcrt.h为UTF-8编码

3.修改\VCLTL\ucrt\10.0.xxxxx.0\中头文件（如stdio.h）可能出现的unicode LTL提示文本，全部删除或修改为UTF8

[hzqst]

以下是修改前和修改后的效果

VCLTL未启用

VCLTL启用

OLLVM编译的

[mingkuang-Chuyu]

谢谢支持，预览版已经支持
https://gitee.com/Chuyu-Team/VC-LTL/releases/3.0.0.4_Preview

[mingkuang-Chuyu]

同理 Clang with Microsoft CodeGen以及Clang 3.7 with Microsoft CodeGen也已经添加完成。