Copy st_other for linker script symbol assignments

Copy st_other for linker script symbol assignments

This fixes a problem seen on powerpc64le ELFv2 when creating a
function symbol alias with ld --defsym.  st_other needs to be copied
from the source symbol to the alias in order to set up the local entry
offset for the alias.  I decided to make this change in the generic
ELF code rather than in elf64-ppc.c since it looks like other targets
that use st_other bits might benefit too.

bfd/
	* elflink.c (_bfd_elf_copy_link_hash_symbol_type): Copy st_other
	bits from source to dest.
	* linker.c (_bfd_generic_copy_link_hash_symbol_type): Update comment.
	* targets.c (struct bfd_target <_bfd_copy_link_hash_symbol_type>):
	Likewise.
	* bfd-in2.h: Regenerate.
ld/testsuite/
	* ld-powerpc/defsym.s, * ld-powerpc/defsym.d: New test.
	* ld-powerpc/powerpc.exp: Run it.