Old versions of aCC need a special compiler flag to get full C++98 template
support as e.g. CMake itself or the Complex and ComplexOneConfig tests need.
The same versions need a special flag to get a proper C++ library, too.
This teaches CMake to detect implicit link information for C, C++, and
Fortran compilers. We detect the implicit linker search directories and
implicit linker options for UNIX-like environments using verbose output
from compiler front-ends. We store results in new variables called
CMAKE_<LANG>_IMPLICIT_LINK_LIBRARIES
CMAKE_<LANG>_IMPLICIT_LINK_DIRECTORIES
The implicit libraries can contain linker flags as well as library
names.