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/assert.cpp

@@ -0,0 +1,9 @@
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void __assert_fail(const char* expr, const char* file, int line, const char* func)
+{
+	fprintf(stderr, "assert: %s:%d: %s: Assertion '%s' failed.\n", file, line, func, expr);
+	abort();
+}