Close #24508: Backport the 3.5 MSBuild project files.

The old project files move to PC/VS9.0 and remain supported.

VS2008 is still required to build 2.7; VS2010 (or later, plus Windows SDK 7.1)
is *also* required to use the new project files.
diff --git a/PCbuild/_multiprocessing.vcxproj b/PCbuild/_multiprocessing.vcxproj
new file mode 100644
index 0000000..3a71c17
--- /dev/null
+++ b/PCbuild/_multiprocessing.vcxproj
@@ -0,0 +1,88 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <ItemGroup Label="ProjectConfigurations">
+    <ProjectConfiguration Include="Debug|Win32">
+      <Configuration>Debug</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|x64">
+      <Configuration>Debug</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|Win32">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|x64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|Win32">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|x64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|Win32">
+      <Configuration>Release</Configuration>
+      <Platform>Win32</Platform>
+    </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|x64">
+      <Configuration>Release</Configuration>
+      <Platform>x64</Platform>
+    </ProjectConfiguration>
+  </ItemGroup>
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>{9E48B300-37D1-11DD-8C41-005056C00008}</ProjectGuid>
+    <RootNamespace>_multiprocessing</RootNamespace>
+    <Keyword>Win32Proj</Keyword>
+  </PropertyGroup>
+  <Import Project="python.props" />
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
+  <PropertyGroup Label="Configuration">
+    <ConfigurationType>DynamicLibrary</ConfigurationType>
+    <CharacterSet>NotSet</CharacterSet>
+  </PropertyGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.props" />
+  <PropertyGroup>
+    <TargetExt>.pyd</TargetExt>
+  </PropertyGroup>
+  <ImportGroup Label="ExtensionSettings">
+  </ImportGroup>
+  <ImportGroup Label="PropertySheets">
+    <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
+    <Import Project="pyproject.props" />
+  </ImportGroup>
+  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup>
+    <_ProjectFileVersion>10.0.30319.1</_ProjectFileVersion>
+  </PropertyGroup>
+  <ItemDefinitionGroup>
+    <Link>
+      <AdditionalDependencies>ws2_32.lib;%(AdditionalDependencies)</AdditionalDependencies>
+      <BaseAddress>0x1e1D0000</BaseAddress>
+    </Link>
+  </ItemDefinitionGroup>
+  <ItemGroup>
+    <ClInclude Include="..\Modules\_multiprocessing\multiprocessing.h" />
+    <ClInclude Include="..\Modules\_multiprocessing\connection.h" />
+  </ItemGroup>
+  <ItemGroup>
+    <ClCompile Include="..\Modules\_multiprocessing\multiprocessing.c" />
+    <ClCompile Include="..\Modules\_multiprocessing\pipe_connection.c" />
+    <ClCompile Include="..\Modules\_multiprocessing\semaphore.c" />
+    <ClCompile Include="..\Modules\_multiprocessing\socket_connection.c" />
+    <ClCompile Include="..\Modules\_multiprocessing\win32_functions.c" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="pythoncore.vcxproj">
+      <Project>{cf7ac3d1-e2df-41d2-bea6-1e2556cdea26}</Project>
+      <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
+    </ProjectReference>
+  </ItemGroup>
+  <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
+  <ImportGroup Label="ExtensionTargets">
+  </ImportGroup>
+</Project>