gdb: make target_ops::make_corefile_notes return a unique ptr

gdb: make target_ops::make_corefile_notes return a unique ptr

Since we converted gdbarch_make_corefile_notes to returning a
gdb::unique_xmalloc_ptr, I figured it would make sense to converted
target_ops::make_corefile_notes as well.

The only implementation of that is in procfs.c, and it should ideally be
re-written as a gdbarch method (see comment in write_gcore_file_1), but
in the mean time I guess it doesn't hurt to throw some unique pointer at
it.

I tested that it builds on Solaris 11 (gcc compile farm machine gcc211),
but I am not able to test it, because I can't get GDB to start a
process (I'll look at that separately).

gdb/ChangeLog:

	* target.h (struct target_ops) <make_corefile_notes>:
	Change return type to unique pointer.
	* target.c (dummy_make_corefile_notes): Likewise.
	* exec.c (struct exec_target) <make_corefile_notes>:
	Likewise.
	(exec_target::make_corefile_notes): Likewise.
	* procfs.c (class procfs_target) <make_corefile_notes>:
	Likewise.
	(procfs_do_thread_registers): Adjust to unique pointer.
	(struct procfs_corefile_thread_data): Add constructor.
	<note_data>: Change type to unique pointer.
	(procfs_corefile_thread_callback): Adjust to unique pointer.
	(procfs_target::make_corefile_notes): Change return type to
	unique pointer.
	* target-delegates.c: Re-generate.
	* gcore.c (write_gcore_file_1): Adjust.
	* target-debug.h (target_debug_print_gdb_unique_xmalloc_ptr_char):
	New.

Change-Id: I768fb17ac0f7adc67d2fe95e952c784fe0ac37ab