calling _dl_start, using GOTOFF access.

	* configure.in (libc_cv_z_execstack): New check.
	* configure: Regenerated.
	* config.make.in (have-z-execstack): New variable set by it.
	* elf/tst-execstack.c: New file.
	* elf/tst-execstack-mod.c: New file.
	* elf/tst-execstack-needed.c: New file.
	* elf/Makefile (tests-execstack-yes, modules-execstack-yes): New
	variables.
	(tests, modules-names): Conditionally include them.
	(distribute): Add tst-execstack-mod.c here.
	($(objpfx)tst-execstack, $(objpfx)tst-execstack.out): New targets.
	(LDFLAGS-tst-execstack, LDFLAGS-tst-execstack-mod): New variables.
	($(objpfx)tst-execstack-needed): New target.
	(LDFLAGS-tst-execstack-needed): New variable.

	* sysdeps/generic/ldsodefs.h (struct rtld_global): Add _dl_stack_flags
	and _dl_make_stack_executable_hook.  Declare _dl_make_stack_executable.
	* elf/rtld.c (_rtld_global): Add initializer for _dl_stack_flags.
	(dl_main): Reset _dl_stack_flags according to PT_GNU_STACK phdr.
	Initialize _dl_make_stack_executable_hook.
	* elf/dl-support.c: Define those new variables.
	(_dl_non_dynamic_init): Scan phdrs for PT_GNU_STACK.
	(_dl_phdr): Fix type.
	* elf/dl-load.c (_dl_map_object_from_fd): Grok PT_GNU_STACK phdr and
	enable execute permission for the stack if necessary.
	* sysdeps/generic/dl-execstack.c: New file.
	* elf/Makefile (dl-routines): Add it.
	* elf/Versions (ld: GLIBC_PRIVATE): Add _dl_make_stack_executable.
	* sysdeps/unix/sysv/linux/dl-execstack.c: New file.