Implement PowerPC64 .localentry for value 1

Implement PowerPC64 .localentry for value 1

This adds support for ".localentry 1", a new st_other
STO_PPC64_LOCAL_MASK encoding that signifies a function with a single
entry point like ".localentry 0", but unlike a ".localentry 0"
function does not preserve r2.

include/
	* elf/ppc64.h: Specify byte offset to local entry for values
	of two to six in STO_PPC64_LOCAL_MASK.  Clarify r2 return
	value for such functions when entering via global entry point.
	Specify meaning of a value of one in STO_PPC64_LOCAL_MASK.
bfd/
	* elf64-ppc.c (ppc64_elf_size_stubs): Use a ppc_stub_long_branch_r2off
	for calls to symbols with STO_PPC64_LOCAL_MASK bits set to 1.
gas/
	* config/tc-ppc.c (ppc_elf_localentry): Allow .localentry values
	of 1 and 7 to directly set value into STO_PPC64_LOCAL_MASK bits.
ld/testsuite/
	* ld-powerpc/elfv2.s: Add .localentry f5,1 testcase.
	* ld-powerpc/elfv2exe.d: Update.
	* ld-powerpc/elfv2so.d: Update.