S/390: Add support for pgste marker

S/390: Add support for pgste marker

This patch adds a new S/390 specific segment type: PT_S390_PGSTE.  For
binaries marked with that segment the kernel will allocate 4k page
tables.  The only user so far will be qemu.

ld/ChangeLog:

2017-06-23  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* Makefile.in: Add s390.em as build dependency.
	* emulparams/elf64_s390.sh (EXTRA_EM_FILE): Add s390.em.
	* emultempl/s390.em: New file.
	* gen-doc.texi: Add documentation for --s390-pgste option.
	* ld.texinfo: Likewise.

include/ChangeLog:

2017-06-23  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* elf/s390.h (PT_S390_PGSTE): Define macro.

binutils/ChangeLog:

2017-06-23  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* readelf.c (get_s390_segment_type): Add support for the new
	segment type PT_S390_PGSTE.
	(get_segment_type): Call get_s390_segment_type.

elfcpp/ChangeLog:

2017-06-23  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* elfcpp.h (enum PT): Add PT_S390_PGSTE to enum.

bfd/ChangeLog:

2017-06-23  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* elf-s390.h: New file.
	* elf64-s390.c (struct elf_s390_link_hash_table): Add params
	field.
	(elf_s390_additional_program_headers): New function.
	(elf_s390_modify_segment_map): New function.
	(bfd_elf_s390_set_options): New function.
	(elf_backend_additional_program_headers)
	(elf_backend_modify_segment_map): Add macro definitions.