ELF/BFD: Handle both variants of the 64-bit Linux core PRPSINFO note

ELF/BFD: Handle both variants of the 64-bit Linux core PRPSINFO note

Fix commit 70a38d42c5b3 ("New entry points for writing Linux NT_PRPSINFO
notes."), <https://sourceware.org/ml/binutils/2013-02/msg00023.html>,
and handle both variants of the 64-bit Linux core PRPSINFO note across
all targets.

The 64-bit Linux core PRPSINFO note matches the 64-bit kernel structure,
defined as follows:

(gdb) ptype struct elf_prpsinfo
type = struct elf_prpsinfo {
    char pr_state;
    char pr_sname;
    char pr_zomb;
    char pr_nice;
    unsigned long pr_flag;
    __kernel_uid_t pr_uid;
    __kernel_gid_t pr_gid;
    pid_t pr_pid;
    pid_t pr_ppid;
    pid_t pr_pgrp;
    pid_t pr_sid;
    char pr_fname[16];
    char pr_psargs[80];
}
(gdb)

where the individual data types of most members are the same across all
64-bit Linux ports, with the exception of `__kernel_uid_t' and
`__kernel_gid_t'.  These are defined in <asm-generic/posix_types.h> as
32-bit `unsigned int' by default, however overridden as 16-bit `unsigned
short' in port-specific <asm/posix_types.h> for the SuperH target.

The default is already handled, as from the commit referred.  Add the
other variant then and provide a backend flag to switch between the two
cases possible, with the 32-bit one being the default and the 16-bit one
explicitly selected.  Set the flag in the SuperH target backend.  This
arrangement is analogous to how the 32-bit Linux core PRPSINFO note is
handled.

	bfd/
	* elf-bfd.h (elf_backend_data): Add `linux_prpsinfo64_ugid16'
	member.
	* elf-linux-core.h (elf_external_linux_prpsinfo64): Rename to...
	(elf_external_linux_prpsinfo64_ugid32): ... this.
	(swap_linux_prpsinfo32_out): Rename to...
	(swap_linux_prpsinfo32_ugid32_out): ... this.
	(elf_external_linux_prpsinfo64_ugid16): New structure.
	(swap_linux_prpsinfo64_ugid16_out): New function.
	* elfxx-target.h [!elf_backend_linux_prpsinfo64_ugid16]
	(elf_backend_linux_prpsinfo64_ugid16): Define.
	(elfNN_bed): Initialize `linux_prpsinfo64_ugid16' member.
	* elf.c (elfcore_write_linux_prpsinfo64): Handle both variants
	of the 64-bit Linux core PRPSINFO note.
	* elf64-sh64.c (elf_backend_linux_prpsinfo64_ugid16): Define.