Help: Revise cmake-buildsystem.7 manual draft

Tweak some wording and cross-references.  Wrap some paragraphs
with long lines.
Merge topic 'cmake-buildsystem-manual' into next

d3c7080 Help: Revise cmake-buildsystem.7 manual draft
Fix wording of "the the" typos throughout text
Merge topic 'fix-text-typos' into next

9e41eb6 Fix wording of "the the" typos throughout text
CMake Nightly Date Stamp
add_dependencies: Disallow use with INTERFACE_LIBRARY.
Style: Use this-> when invoking member function.
install: Rename variable referencing cmake version.

The next version is 3.0.0, not 2.8.13.

The version generated in the export file should be updated in
the release branch in both cmExportInstallFileGenerator and
cmExportBuildFileGenerator.
cmTarget: Rename container holding link implementation objects.

Don't erroneously name it for the link implementation. That's
something different.
Help: Remove workaround for pre-CMake 2.8.4 code.

The requirement was updated in commit 920ffbf5 (Require CMake 2.8.4
or greater to build CMake, 2013-10-11) and similar snippets were
removed.
Help: Workaround pygments reporting an error for genexes.

Without the workaround, CMake code snippets are not highlighted
at all because pygments can not lex the generator expressions.
export: Only generate and install configuration files if needed.

The modern way to create configuration dependent content is using
generator expressions in the main export file.  The only non-deprecated
property still generated in the configuration-specific files are
IMPORTED_LOCATION_<CONFIG>

INTERFACE_LIBRARY targets have no location, and no need for those
files.
install: Ensure that install(TARGETS) works with no DESTINATION

INTERFACE_LIBRARY targets have no corresponding files, and so
require no DESTINATION to install anything to.
get_property: Fix testing ALIASED_TARGET target property (#14670)

In the case where the argument is not an ALIAS, the variable should
be set to a -NOTFOUND content.
Run the add_compile_options command unit test.

This has not been executed since it was added in
commit a984f325 (Introduce add_compile_options command., 2013-06-04).
cmTarget: Don't update IMPORTED target compilation properties

The include_directories() and add_compile_options() commands
should not append to the corresponding target property for IMPORTED
targets.  This is already the case for add_definitions().
GenerateExportHeader: Reformat docs.
Help: Mark some code blocks as containing cmake code.
Help: Reformat Qt autogenerator documentation.
cmTarget: Fix the property compatibility error message

Don't refer to 'both', but a 'mixture'. List all compatible interface
property types possible.

Add another test for a mixture of three compatibilities.