Kernel: add support for Windows

src/detection/kernel/kernel_linux.c

@@ -0,0 +1,9 @@
+#include "kernel.h"
+
+void ffDetectKernel(FFinstance* instance, FFKernelResult* result)
+{
+    ffStrbufInit(&result->error);
+    ffStrbufInitS(&result->sysname, instance->state.utsname.sysname);
+    ffStrbufInitS(&result->release, instance->state.utsname.release);
+    ffStrbufInitS(&result->version, instance->state.utsname.version);
+}