The add_library(INTERFACE) and Interface Libraries documentation
list all the INTERFACE_* properties and target_* commands that
can be used to define the interface. Add INTERFACE_SOURCES
and target_sources() to these lists for completeness.
This is the convention suggested in the Sphinx documentation and is
already used in several other places in the CMake documentation.
Update a few places where we were using other characters.
Explain how to use $<BUILD_INTERFACE> and $<INSTALL_INTERFACE> directly
in the documentation of the target_include_directories command and
INTERFACE_INCLUDE_DIRECTORIES target property. Otherwise readers need
to notice the link to the cmake-buildsystem(7) manual and find the
example in that to understand the need for these expressions.
Also fix the explanation in cmake-buildsystem(7) to not claim that
relative paths may be used inside a BUILD_INTERFACE expression.
People will be tempted to put things there for convenience, thereby
causing conflicts similar to
http://thread.gmane.org/gmane.comp.compilers.clang.devel/35162/focus=35169
where it is conceivable that the LLVM developers could put a flag on
a target for convenience, which would cause conflicts for some downstreams.
Describe how to define a buildsystem of binary targets, how to
express dependencies between them, how to add build specifications,
how to specify usage requirements, transitive and compatible
propagation and the various pseudo targets.