Address space creation/deletion implemented

- Proper releasing of user pmd and pgds when a space is not used.
- Proper releasing of task, space ids.

- At occasions a starting thread gets bogus SPSR, this needs investigating.
- At a very rare occasion arch_setup_new_thread() had a kernel data abort during
  register copying from one task to another. Needs investigating.

include/l4/arch/arm/v5/mm.h

@@ -138,6 +138,7 @@ void add_section_mapping_init(unsigned int paddr, unsigned int vaddr,
 			      unsigned int size, unsigned int flags);
 
 struct address_space;
+int delete_page_tables(struct address_space *space);
 int copy_user_tables(struct address_space *new, struct address_space *orig);
 pgd_table_t *copy_page_tables(pgd_table_t *from);
 void remap_as_pages(void *vstart, void *vend);