Revert "Async-signal safe TLS."

This reverts commit 7f507ee17a.

Conflicts:
	ChangeLog
	nptl/tst-tls7.c
	nptl/tst-tls7mod.c

elf/dl-open.c

@@ -548,10 +548,7 @@ cannot load any more object with static TLS"));
 	     generation of the DSO we are allocating data for.  */
 	  _dl_update_slotinfo (imap->l_tls_modid);
 #endif
-	  /* We do this iteration under a signal mask in dl-reloc; why not
-	     here?  Because these symbols are new and dlopen hasn't
-	     returned yet.  So we can't possibly be racing with a TLS
-	     access to them from another thread.  */
+
 	  GL(dl_init_static_tls) (imap);
 	  assert (imap->l_need_tls_init == 0);
 	}