cmake_add_fortran_directory uses imported targets when using the
mingw fortran compiler. This change makes those targets global
in scope so they act just like the real targets that exist when
a fortran compiler exists and regular add_subdirectory is used.
Fix the implementation to allow full paths with spaces. Change the
interpretation of relative paths to be with respect to the current binary
directory. This matches the convention used in ExternalProject. Test
both full and relative paths in the VSGNUFortran test.
This patch adds a new module that allows for easy integration of MinGW
gfortran and the Visual Studio compiler. It is done in a function called
cmake_add_fortran_subdirectory. The patch also includes a test for this
feature.
