Move C source code into subfolder

autoformat.sh

meson.build

minimal_build.sh

waypipe-c/bench.c

waypipe-c/client.c

waypipe-c/dmabuf.c

waypipe-c/dmabuf.h

waypipe-c/handlers.c

waypipe-c/interval.c

waypipe-c/interval.h

waypipe-c/kernel.c

waypipe-c/kernel.h

waypipe-c/kernel_avx2.c

waypipe-c/kernel_avx512f.c

waypipe-c/kernel_neon.c

waypipe-c/kernel_sse3.c

waypipe-c/main.h

waypipe-c/mainloop.c

waypipe-c/meson.build

waypipe-c/parsing.c