[ARM] Implement FDPIC relocations.

[ARM] Implement FDPIC relocations.

This is the main BFD patch, that enables the linker to actually handle
the FDPIC relocations.

2018-04-25  Christophe Lyon  <christophe.lyon@st.com>
	Mickaël Guêné  <mickael.guene@st.com>

	bfd/
	* elf32-arm.c (struct fdpic_local): New.
	(elf_arm_obj_tdata): Add local_fdpic_cnts field.
	(elf32_arm_local_fdpic_cnts): New.
	(struct fdpic_global): New.
	(elf32_arm_link_hash_entry): Add fdpic_cnts field.
	(elf32_arm_link_hash_table): Add srofixup field.
	(arm_elf_add_rofixup): New.
	(arm_elf_fill_funcdesc): New.
	(elf32_arm_link_hash_newfunc): Handle fdpic_cnts.
	(elf32_arm_allocate_local_sym_info): Likewise.
	(create_got_section): Create .rofixup section.
	(elf32_arm_copy_indirect_symbol): Handle fdpic_cnts.
	(bfd_elf32_arm_set_target_params): Handle FDPIC.
	(elf32_arm_final_link_relocate): Likewise.
	(elf32_arm_check_relocs): Likewise.
	(allocate_dynrelocs_for_symbol): Likewise.
	(elf32_arm_size_dynamic_sections): Likewise.
	(elf32_arm_finish_dynamic_sections): Likewise.
	(elf32_arm_output_arch_local_syms): Likewise.
	(elf32_arm_fdpic_omit_section_dynsym): New.

	ld/
	* emulparams/armelf_linux_fdpiceabi.sh: Add .rofixup section.