Add a convenient way to add the includes install dir to the INTERFACE.

Export the INCLUDES DESTINATION without appending to the
INTERFACE_INCLUDE_DIRECTORIES of the target itself. That way, a target
can be exported multiple times with different INCLUDES DESTINATION
without unintended cross-pollution of export sets.
FindQt4: Populate the INTERFACE_LINK_LIBRARIES of IMPORTED targets.

This makes the IMPORTED_LINK_INTERFACE_LIBRARIES_<CONFIG> properties
obsolete.
Check*CompilerFlag: Document use of CMAKE_REQUIRED_DEFINITIONS (#14309)

Explain how CMAKE_REQUIRED_DEFINITIONS is set before calling the
check_*_source_compiles macros.
Genex: Allow relative paths in INSTALL_INTERFACE.

These paths can be prepended with the ${_IMPORT_PREFIX} generated
in the export file.

Such relative paths were previously an error.
cmTarget: Fix property name typo in docs.
sha2: Avoid type-punned pointer dereference (#14314)

GCC warns:

 dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]

on constructs like

 *(sha_word64*)&var =

so use memcpy to perform such assignments instead.
Merge topic 'sha2-avoid-type-pun'

6a365d0 sha2: Avoid type-punned pointer dereference (#14314)
Merge topic 'doc-check-compiler-flag-override'

3e79d65 Check*CompilerFlag: Document use of CMAKE_REQUIRED_DEFINITIONS (#14309)
Merge topic 'Qt4-INTERFACE_LINK_LIBRARIES'

0f267c0 FindQt4: Populate the INTERFACE_LINK_LIBRARIES of IMPORTED targets.
Merge topic 'install-interface-includes'

650e61f Add a convenient way to add the includes install dir to the INTERFACE.
Merge topic 'install-interface-relative'

d777b8e Genex: Allow relative paths in INSTALL_INTERFACE.
Merge topic 'tid-system-argument'

9b9a596 cmTarget: Fix property name typo in docs.