FindOpenGL: Revert support for imported targets (#15267)

Revert the feature added by commit v3.1.0-rc1~420^2~2 (FindOpenGL:
Provide imported targets for GL and GLU, 2014-05-31).  Unfortunately it
does not work on Windows because the full path to each library file is
not actually known.  The IMPORTED_LOCATION of an imported target must be
a full path, but OPENGL_gl_LIBRARY is just 'opengl32' on Windows because
the actual library file is in some implicit link directory that we may
know know.

More infrastructure will be needed in CMake to allow a name-only
imported library.  Until that exists, we will not be able to provide
imported targets in FindOpenGL.
FindPythonInterp: fix version component variables for Python 1.4 (#15275)

This bug was introduced in "FindPythonInterp: rework the version detection"
7d6db93de9ffc6e6092fa722aaf9c057dadcd634.
Merge branch 'FindPythonInterp-Fix-1.4' into release
Merge branch 'FindOpenGL-revert-imported-targets' into release
Help: Document Nsight Tegra toolchain configuration (#15276)
CPackIFW: Correction of the module documentation
VS, WINCE: Fix entry point for Unicode builds

When _UNICODE is defined VS uses wmain instead of main as the entry function.
To make this correctly work on WindowsCE EntryPointSymbol needs to be set to
mainWCRTStartup instead of mainACRTStartup for console applications and to
wWinMainCRTStartup instead of WinMainCRTStartup for GUI applications.

Signed-off-by: Pascal Bach <pascal.bach@siemens.com>
Merge branch 'fix-wince-unicode-entry-point' into release
Help: Fix typo in CMAKE_CXX_KNOWN_FEATURES docs

Typo "ss defined" => "as defined".
VS: Add source file properties to set the hlsl shader entry point and model

Create properties VS_SHADER_ENTRYPOINT and VS_SHADER_MODEL.  Without
these many .hlsl source files may not be possible to use.  Extend the
VSWinStorePhone test project to cover them.
Merge branch 'doc-Nsight-Tegra-toolchain' into release
Merge branch 'CPackIFW-doc-typos' into release
Merge branch 'doc-CMAKE_CXX_KNOWN_FEATURES-typo' into release
Merge branch 'vs-hlsl-settings' into release