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/cat/CMakeLists.txt

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

userspace/programs/cat/main.cpp

@@ -0,0 +1,50 @@
+#include <fcntl.h>
+#include <stdio.h>
+
+bool cat_file(int fd)
+{
+	char last = '\0';
+	char buffer[1024];
+	while (ssize_t n_read = read(fd, buffer, sizeof(buffer)))
+	{
+		if (n_read == -1)
+		{
+			perror("read");
+			return false;
+		}
+		write(STDOUT_FILENO, buffer, n_read);
+		last = buffer[n_read - 1];
+	}
+	if (last != '\n')
+		write(STDOUT_FILENO, "\n", 1);
+	return true;
+}
+
+int main(int argc, char** argv)
+{
+	int ret = 0;
+
+	if (argc > 1)
+	{
+		for (int i = 1; i < argc; i++)
+		{
+			int fd = open(argv[i], O_RDONLY);
+			if (fd == -1)
+			{
+				perror(argv[i]);
+				ret = 1;
+				continue;
+			}
+			if (!cat_file(fd))
+				ret = 1;
+			close(fd);
+		}
+	}
+	else
+	{
+		if (!cat_file(STDIN_FILENO))
+			ret = 1;
+	}
+
+	return ret;
+}