[vdr] non standard `.c` extension for C++ files

Dear VDR developers,

I am curious why the C++ source files have the extension `.c` and not `.c{c,pp,xx}`.

I am asking because I tried to use `scan-build` from Clang/LLVM and by default – and I did not find an option to change that – it treats `.c` files as C files and not C++.

Running Clang directly on the `.c` files the following message is displayed.

clang: warning: treating 'c' input as 'c++' when in C++ mode, this behavior is deprecated

The folks an #llvm helped me and by verifying this putting

#ifndef __cplusplus #error Not C++ #endif

in a file. Clang can be passed `-x c++` to override that behavior.

In the end I renamed the files and adapted `Makefile` to get `scan-build` working and it did not find any errors.

Thanks,

Paul