Beginning setup to link into code.lib, defined some variables needed for linkage and link tests.
Some #include wrangling, and removal of some C-style struct declarations that were incompatible with C++ class declarations.
End of linkage work. (This commit is probably temporary)
 * Includes wxfredstubs.cpp to prevent linkage to certain data members and functions defined in freespace.cpp.
 * "_SECURE_SCL" and "_HAS_ITERATOR_DEBUGGING" defines removed from the project files
 * C runtime library (CRT) switched to use DLL so as to integrate with wxWidgets default settings.