Split source into multiple files

SIGUSR1 now causes reload of blacklist
sigstoped now resumes all processes it stoped upon reciving SIGINT or SIGTERM
sigstoped avoids stopping processes that have no top level window left TODO: is this enough?

debug.h

@@ -0,0 +1,10 @@
+#pragma once
+#include <string>
+#include <iostream>
+
+constexpr bool DEBUG = false;
+
+inline void debug(const std::string& in)
+{
+    if constexpr (DEBUG) std::cout<<in<<'\n';
+}