Add include refereces to ../include/fix8 in serveral files in order to be able to compile (e.g. f8dll.h resides in ../include/fix8/ and not in ../include/.
It is "convenient" when header files can be referenced in include statements without the specification of a directory. A few file names were sufficiently unqiue. But some others were chosen for C++ source files that had got the potential to get in conflict with name selections from other software libraries. Your addition of the name "fix8" as a parent directory made their reuse safer.