BuildSystem: Cleanup userspace directory layout

userspace programs are now in userspace/programs
userspace tests are now in userspace/tests

This makes listing userspace projects much cleaner. Libraries were
already separated to their own directory, so other programs should also.

userspace/programs/poweroff/CMakeLists.txt

@@ -0,0 +1,8 @@
+set(SOURCES
+	main.cpp
+)
+
+add_executable(poweroff ${SOURCES})
+banan_link_library(poweroff libc)
+
+install(TARGETS poweroff OPTIONAL)

userspace/programs/poweroff/main.cpp

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/banan-os.h>
+
+void usage(int ret, char* arg0)
+{
+	FILE* fout = (ret == 0) ? stdout : stderr;
+	fprintf(fout, "usage: %s [OPTIONS]...\n", arg0);
+	fprintf(fout, "  -s, --shutdown  Shutdown the system (default)\n");
+	fprintf(fout, "  -r, --reboot    Reboot the system\n");
+	fprintf(fout, "  -h, --help      Show this message\n");
+	exit(ret);
+}
+
+int main(int argc, char** argv)
+{
+	int operation = POWEROFF_SHUTDOWN;
+	for (int i = 1; i < argc; i++)
+	{
+		if (strcmp(argv[i], "-s") == 0 || strcmp(argv[i], "--shutdown") == 0)
+			operation = POWEROFF_SHUTDOWN;
+		else if (strcmp(argv[i], "-r") == 0 || strcmp(argv[i], "--reboot") == 0)
+			operation = POWEROFF_REBOOT;
+		else if (strcmp(argv[i], "-h") == 0 || strcmp(argv[i], "--help") == 0)
+			usage(0, argv[0]);
+		else
+			usage(1, argv[0]);
+	}
+
+	if (poweroff(operation) == -1)
+	{
+		perror("poweroff");
+		return 1;
+	}
+
+	return 0;
+}