PR ld/15787

	PR ld/15787
	* elf32-arm.c (elf32_arm_final_link_relocate): Use origin of output
	segment containing the relocating symbol instead of assuming 0 for
	sb group relocations.

	* ld-arm/group-relocs-ldr-bad.s: Redefine bar into foo section
	beyond 16 bit offset width.
	* ld-arm/group-relocs-ldrs-bad.s: Likewise.
	* ld-arm/group-relocs-ldr-bad.d: Adjust expected result.
	* ld-arm/group-relocs-ldrs-bad.d: Likewise.
	* ld-arm/group-relocs.s: Add comments.  Move symbols used for sb
	group relocations into .data section.  Drop section zero.  Use pc/r0
	as base register when pc/sb group relocations are used.
	* ld-arm/group-relocs.d: Adjust expected result.
	* ld-arm/group-relocs-alu-bad-2.d: New test for sb group relocation.
	* ld-arm/group-relocs-ldc-bad-2.d: Likewise.
	* ld-arm/group-relocs-ldr-bad-2.d: New test for pc group relocation.
	* ld-arm/group-relocs-ldrs-bad-2.d: Likewise.
	* ld-arm/unresolved-2.d: Add sb relocation failure test.
	* ld-arm/group-relocs-alu-bad-2.s: New test source.
	* ld-arm/group-relocs-ldr-bad-2.s: Likewise.
	* ld-arm/group-relocs-ldrs-bad-2.s: Likewise.
	* ld-arm/group-relocs-ldc-bad-2.s: Likewise.
	* ld-arm/unresolved-2.s: Likewise.
	* ld-arm/arm-elf.exp: For group-relocs, drop section zero start
	definition.  Run the new tests.