try_compile: Restore expansion of ;-list in COMPILE_DEFINITIONS

The quoting added by commit 8c5221fb1f (try_compile: Preserve special
characters in COMPILE_DEFINITIONS, 2019-01-21, v3.14.0-rc1~108^2~3)
broke the case that the `COMPILE_DEFINITIONS` value contains a `;`.
Without the quoting the `;` would be generated literally in an unquoted
argument in the test `CMakeLists.txt` file and would then be expanded.
With quoting the `;` is preserved, which is not the old behavior.

Fix this by expanding the `;`-list ahead of time.  Add test cases for
behavior with both `#` and `;`.

This was noticed with the PGI compiler where we set
`CMAKE_CXX*_STANDARD_COMPILE_OPTION` to values like `--c++17;-A`.  The
symptom had also been observed while preparing commit ef8f237686
(ParseImplicitIncludeInfo: add SunPro Fortran and PGI compiler, Cray
fix, 2019-01-29, v3.14.0-rc1~26^2~2) but was not recognized at the time
as a regression.  Revert the workaround added by that commit.

Fixes: #18919

Source/cmCoreTryCompile.cxx

@@ -226,7 +226,7 @@ int cmCoreTryCompile::TryCompileCode(std::vector<std::string> const& argv,
     } else if (doing == DoingCMakeFlags) {
       cmakeFlags.push_back(argv[i]);
     } else if (doing == DoingCompileDefinitions) {
-      compileDefs.push_back(argv[i]);
+      cmSystemTools::ExpandListArgument(argv[i], compileDefs);
     } else if (doing == DoingLinkOptions) {
       linkOptions.push_back(argv[i]);
     } else if (doing == DoingLinkLibraries) {