Add _testclinic_limited project to the Visual Studio solution:
* In "PCbuild/", copy "_asyncio.vcxproj" to "_testclinic_limited.vcxproj",
replace "RootNamespace" with "_testclinic_limited", replace "_asyncio.c"
with "_testclinic_limited.c".
* Open Visual Studio, open "PCbuild\pcbuild.sln", add the existing
"PCbuild\_testclinic_limited.vcxproj" project to the solution.
* Add a dependency from "python" project to the "_testclinic_limited"
project.
* Save and exit Visual Studio.
* Add ";_testclinic_limited" to "<TestModules Include="...">"
in "PCbuild\pcbuild.proj".
