Add the function cmake_expand_imported_targets() to expand imported
targets in a list of libraries into their on-disk file names for a
particular configuration. Adapt the implementation from KDE's
HANDLE_IMPORTED_TARGETS_IN_CMAKE_REQUIRED_LIBRARIES which has been in
use for over 2 years. Call the function from all the Check*.cmake
macros to handle imported targets named in CMAKE_REQUIRED_LIBRARIES.
Alex
This check if the function exists and the prototype we want to use is
correct. There are still functions which have different prototypes on
different UNIX systems.
Alex Neundorf
Andreas Schneider