BuildSystem: Move all userpace libraries under the userspace directory

As the number of libraries is increasing, root directory starts to
expand. This adds better organization for libraries

userspace/libraries/LibC/sys/select.cpp

@@ -0,0 +1,31 @@
+#include <sys/select.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+int pselect(int nfds, fd_set* __restrict readfds, fd_set* __restrict writefds, fd_set* __restrict errorfds, const struct timespec* __restrict timeout, const sigset_t* __restrict sigmask)
+{
+	sys_pselect_t arguments {
+		.nfds = nfds,
+		.readfds = readfds,
+		.writefds = writefds,
+		.errorfds = errorfds,
+		.timeout = timeout,
+		.sigmask = sigmask
+	};
+	return syscall(SYS_PSELECT, &arguments);
+}
+
+int select(int nfds, fd_set* __restrict readfds, fd_set* __restrict writefds, fd_set* __restrict errorfds, struct timeval* __restrict timeout)
+{
+	timespec* pts = nullptr;
+	timespec ts;
+	if (timeout)
+	{
+		ts.tv_sec = timeout->tv_sec;
+		ts.tv_nsec = timeout->tv_usec * 1000;
+		pts = &ts;
+	}
+
+	// TODO: "select may update timeout", should we?
+	return pselect(nfds, readfds, writefds, errorfds, pts, nullptr);
+}