objcopy renaming section with explicit flags

objcopy renaming section with explicit flags

This tidies SEC_RELOC handling in bfd, in the process fixing a bug
with objcopy when renaming sections.

bfd/
	* reloc.c (_bfd_generic_set_reloc): Set/clear SEC_RELOC depending
	on reloc count.
	* elf64-sparc.c (elf64_sparc_set_reloc): Likewise.
binutils/
	* objcopy.c (copy_relocations_in_section): Remove now unnecessary
	clearing of SEC_RELOC.
	* testsuite/binutils-all/rename-section-01.d: New test.
	* testsuite/binutils-all/objcopy.exp: Run it.
gas/
	* write.c (size_seg): Remove unneccesary twiddle of SEC_RELOC.
	(write_relocs): Likewise.  Always call bfd_set_reloc.