* elf/dl-tls.c (__tls_get_addr): After calling _dl_update_slotinfo

	refetch dtv, as it might have changed.
	* elf/Makefile: Add rules to build and run tst-tls18.
	* elf/tst-tls18.c: New test.
	* elf/tst-tlsmod18a.c: New file.