* target.c (target_read): Stop if target_read_partial returns 0

	* target.c (target_read): Stop if target_read_partial returns 0
	when some bytes have already been read.
	(target_write): Likewise for target_write_partial.
	(target_read_partial, target_write_partial): Make static.
	(target_read_alloc): New.
	* target.h: Doc fixes.
	(target_read_partial, target_write_partial): Delete prototypes.
	(target_read_alloc): New prototype.

	* auxv.c (target_auxv_read): Delete.
	(target_auxv_search, fprint_target_auxv): Use target_read_alloc.
	* auxv.h (target_auxv_read): Delete prototype.
	* avr-tdep.c (avr_io_reg_read_command): Use target_read_alloc.
	* ia64-tdep.c (getunwind_table, get_kernel_table): Likewise.
	* linux-nat.c (linux_nat_make_corefile_notes): Likewise.
	* procfs.c (procfs_make_note_section): Likewise.
	* remote.c (remote_xfer_partial): Don't loop here.
	* sparc-tdep.c (sparc_fetch_wcookie): Use target_read.