CMP0022: Add unit test for null pointer check and message.
Merge branch 'master' into next
Makefile: Always create clean target command

Borland Make complains if the phony clean target has no rule to build it.
If there are no files to clean, generate and run an empty clean script.
Create make rules for INTERFACE_LIBRARY targets.

The result is that the depends of the target are created.

So,

 add_library(somelib foo.cpp)
 add_library(anotherlib EXCLUDE_FROM_ALL foo.cpp)
 add_library(extra EXCLUDE_FROM_ALL foo.cpp)
 target_link_libraries(anotherlib extra)

 add_library(iface INTERFACE)
 target_link_libraries(iface INTERFACE anotherlib)

Executing 'make iface' will result in the anotherlib and extra targets
being made.

Adding a regular executable to the INTERFACE of an INTERFACE_LIBRARY
will not result in the executable being built with 'make iface' because
of the logic in cmComputeTargetDepends::AddTargetDepend.

So far, this is implemented only for the Makefile generator. Other
generators will follow if this feature is possible for them.
Merge topic 'update-kwsys'

0408415 Merge branch 'upstream-kwsys' into update-kwsys
c01e744 KWSys 2013-10-15 (6eab64c3)
CMP0022: Add unit test for null pointer check and message.
Merge topic 'INTERFACE_LIBRARY-build-targets' into next

c9ee149 Create make rules for INTERFACE_LIBRARY targets.
dba4962 Makefile: Always create clean target command
Merge topic 'print-CMP0022-content-conflict-test' into next

6d0ec4a CMP0022: Add unit test for null pointer check and message.
Merge topic 'print-CMP0022-content-conflict-test' into next

4fd6024 CMP0022: Add unit test for null pointer check and message.