Provide mprotect syscall

elf/Versions

 libc {
   GLIBC_2.0 {
 %ifdef EXPORT_UNWIND_FIND_FDE
     __register_frame_info; __deregister_frame_info;
 %endif
   }
   GLIBC_2.1 {
     # functions used in other libraries
     _dl_mcount_wrapper; _dl_mcount_wrapper_check;
   }
@@ skipping 75 matching lines @@
     __nacl_irt_exit;
     __nacl_irt_mkdir;
     __nacl_irt_rmdir;
     __nacl_irt_chdir;
     __nacl_irt_getcwd;
     __nacl_irt_fstat;
     __nacl_irt_getdents;
     __nacl_irt_gettod;
     __nacl_irt_mmap;
     __nacl_irt_munmap;
+    __nacl_irt_mprotect;
     __nacl_irt_mutex_create;
     __nacl_irt_mutex_destroy;
     __nacl_irt_mutex_lock;
     __nacl_irt_mutex_trylock;
     __nacl_irt_mutex_unlock;
     __nacl_irt_nanosleep;
     __nacl_irt_open;
     __nacl_irt_open_resource;
     __nacl_irt_read;
     __nacl_irt_write;
@@ skipping 42 matching lines @@
     _dl_allocate_tls; _dl_deallocate_tls;
     _dl_get_tls_static_info; _dl_allocate_tls_init;
     _dl_tls_setup; _dl_rtld_di_serinfo;
     _dl_make_stack_executable;
     # Only here for gdb while a better method is developed.
     _dl_debug_state;
     # Pointer protection.
     __pointer_chk_guard;
   }
 }