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/nslookup/CMakeLists.txt

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

userspace/programs/nslookup/main.cpp

@@ -0,0 +1,54 @@
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#define MAX(a, b) ((a) < (b) ? (b) : (a))
+
+int main(int argc, char** argv)
+{
+	if (argc != 2)
+	{
+		fprintf(stderr, "usage: %s DOMAIN\n", argv[0]);
+		return 1;
+	}
+
+	int socket = ::socket(AF_UNIX, SOCK_SEQPACKET, 0);
+	if (socket == -1)
+	{
+		perror("socket");
+		return 1;
+	}
+
+	sockaddr_un addr;
+	addr.sun_family = AF_UNIX;
+	strcpy(addr.sun_path, "/tmp/resolver.sock");
+	if (connect(socket, (sockaddr*)&addr, sizeof(addr)) == -1)
+	{
+		perror("connect");
+		return 1;
+	}
+
+	if (send(socket, argv[1], strlen(argv[1]), 0) == -1)
+	{
+		perror("send");
+		return 1;
+	}
+
+	sockaddr_storage storage;
+	if (recv(socket, &storage, sizeof(storage), 0) == -1)
+	{
+		perror("recv");
+		return 1;
+	}
+
+	close(socket);
+
+	char buffer[MAX(INET_ADDRSTRLEN, INET6_ADDRSTRLEN)];
+	printf("%s\n", inet_ntop(storage.ss_family, storage.ss_storage, buffer, sizeof(buffer)));
+
+	return 0;
+}