C++: Implement conditional signal handlers based on overrides. This uses templates in a sort of hacky way to determine if our virtual functions have been overridden. Leaving some debug code in for the moment to make sure it works on all platforms. OS/2 will require using GCC for the C++ bindings, since VisualAge only supports C++99 and Watcom doesn't even support that as far as I know.

# Set these here to change the version for all platforms
DW_MAJOR_VERSION=3
DW_MINOR_VERSION=3