Add CMake build file, make biosig optional

[tstenner]

Removing Biosig won't be easy. [..] Changing Biosig to be compatible with VSC won't be easy either, [..] I doubt this is going to happen.

-- someone in #47

[tstenner]

Right now this doesn't build with libbiosig if it's enabled and it still requires libxdf, but adding that should be quite easy once I a local mingw installation.

It also requires https://github.com/xdf-modules/libxdf/pull/20 and libxdf to be present in /libxdf, but there should be a more elegant solution for that, too.

[cbrnr]

🤣 are you saying this already compiles? This is great! I have two questions:

1. I assume building has to be done with cmake and doesn't work with qmake?
2. XDF is the only format SigViewer supports without Biosig, right?

It would also be great to make XDF support optional just like Biosig (so that we can turn off both and SigViewer can't load anything).

In case you take a closer look at the Biosig source code, maybe you can estimate if this will ever compile with VCC?

[tstenner]

are you saying this already compiles?

Compiles, runs, loads and displays a sample XDF file.

I assume building has to be done with cmake and doesn't work with qmake?

qmake would have to define NOBIOSIG in case it's not needed and skip some source files, but otherwise there's no reason it couldn't be done.

XDF is the only format SigViewer supports without Biosig, right?

I'd guess so, but I started developing sigviewer in the late morning so I'm not an expert.

In case you take a closer look at the Biosig source code, maybe you can estimate if this will ever compile with VCC?

biosig heavily depends on iconv, which is part of the posix standard, so mingw already has it. MSVC/Windows, not so much.