... in many places where the function call will later need to be between
modules (or libraries, or the executable) and the annotation will be a necessity
to keep the linkage working on Windows.
That's all that this sweeping commit does.
... Require the declarations to be in .h files, to be sure graph.pl detects the
dependencies.
Only one more #include was needed in Nyquist.cpp. This doesn't reveal any
more hidden cycles.
... except Audacity.h
This forces us to make each header contain all forward declarations or nested
headers that it requires, rather than depend on context.