Don't generate self-references for system include directories.

Targets which link directly to themselves should not result in
generate-time errors (reported by the DAG checker).

Self-links are handled separately with policy CMP0038.
Help: Fix up the VISIBILITY_INLINES_HIDDEN docs.

Resolve some sentence fragments, remove a copy-pasto from other docs
and use a link to the CMAKE_VISIBILITY_INLINES_HIDDEN variable.
Make the cmStrictTargetComparison operate on const cmTarget*.
VS: Add CMAKE_VS_(DEVENV|MSBUILD|MSDEV)_COMMAND variables

Since commit 5f5c92b9 (VS: Add internal APIs to find MSBuild,
devenv/VCExpress, and msdev, 2013-11-13) the VS generators have
known how to lookup the locations of their build tools directly.
Expose this information to CMake language code by defining new
variables to hold the paths to these tools.
CMakeDetermineCompilerId: Use CMAKE_VS_(DEVENV|MSBUILD|MSDEV)_COMMAND

In the code path for launching the VS IDE tools, avoid using
CMAKE_MAKE_PROGRAM.  Instead use the variables CMAKE_VS_DEVENV_COMMAND,
CMAKE_VS_MSBUILD_COMMAND, and CMAKE_VS_MSDEV_COMMAND to lookup the
location of the build tool needed.  Choose the proper tool based on
availability and necessity for the language (e.g. Intel Fortran must
build with devenv.com and not MSBuild.exe).
Merge topic 'cleanup-build-commands'

e420124 CMakeDetermineCompilerId: Use CMAKE_VS_(DEVENV|MSBUILD|MSDEV)_COMMAND
0c55729 VS: Add CMAKE_VS_(DEVENV|MSBUILD|MSDEV)_COMMAND variables
Merge topic 'minor-cleanups'

259bf09 Make the cmStrictTargetComparison operate on const cmTarget*.
8cc3cdb Help: Fix up the VISIBILITY_INLINES_HIDDEN docs.
1396ab8 Don't generate self-references for system include directories.
Tests/Contracts: Update test for VTK release branch

The plan is to reinstate the VTK contracts test so that CMake
& VTK devs will both be made aware when a change in CMake causes
build problems for VTK.
Merge topic 'vtk-contract'

1b173f2 Tests/Contracts: Update test for VTK release branch
Help: Format and clarify source_group() documentation (#14631)

Refine the .rst formatting.  Document the FILES option explicitly
and specify how it treats relative paths.
Merge topic 'doc-source_group-FILES'

0060e95 Help: Format and clarify source_group() documentation (#14631)