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/include/dlfcn.h

@@ -0,0 +1,22 @@
+#ifndef _DLFCN_H
+#define _DLFCN_H 1
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/dlfcn.h.html
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define RTLD_LAZY	1
+#define RTLD_NOW	2
+#define RTLD_GLOBAL	3
+#define RTLD_LOCAL	4
+
+int		dlclose(void* handle);
+char*	dlerror(void);
+void*	dlopen(const char* file, int mode);
+void*	dlsym(void* __restrict handle, const char* __restrict name);
+
+__END_DECLS
+
+#endif