Move server API concept to base framework

This commit introduces the new `Component` interface in the form of the
headers base/component.h and base/entrypoint.h. The os/server.h API
has become merely a compatibilty wrapper and will eventually be removed.
The same holds true for os/signal_rpc_dispatcher.h. The mechanism has
moved to base/signal.h and is now called 'Signal_handler'.

Since the patch shuffles headers around, please do a 'make clean' in the
build directory.

Issue #1832

repos/base-linux/src/test/lx_hybrid_pthread_ipc/main.cc

@@ -12,11 +12,14 @@
  */
 
 /* Genode includes */
+#include <base/component.h>
 #include <base/thread.h>
 #include <base/printf.h>
 
 /* libc includes */
 #include <pthread.h>
+#include <stdlib.h>
+
 
 
 static Genode::Lock *main_wait_lock()
@@ -46,7 +49,18 @@ static void *pthread_entry(void *)
 }
 
 
-int main(int, char **)
+static int exit_status;
+static void exit_on_suspended() { exit(exit_status); }
+
+
+Genode::size_t Component::stack_size() { return 16*1024*sizeof(long); }
+char const * Component::name()         { return "lx_hybrid_pthread_ipc"; }
+
+
+/*
+ * Component implements classical main function in construct.
+ */
+void Component::construct(Genode::Environment &env)
 {
 	Genode::printf("--- pthread IPC test ---\n");
 
@@ -58,5 +72,6 @@ int main(int, char **)
 	main_wait_lock()->lock();
 
 	Genode::printf("--- finished pthread IPC test ---\n");
-	return 0;
+	exit_status = 0;
+	env.ep().schedule_suspend(exit_on_suspended, nullptr);
 }