remote: consider addressable unit size when reading/writing memory

remote: consider addressable unit size when reading/writing memory

Adapt code in remote.c to take into account addressable unit size when
reading/writing memory.

A few variables are renamed and suffixed with _bytes or _units. This
way, it's more obvious if there is any place where we add or compare
values of different kinds (which would be a mistake).

gdb/ChangeLog:

	* common/rsp-low.c (needs_escaping): New.
	(remote_escape_output): Add unit_size parameter. Refactor to
	support multi-byte addressable units.  Rename parameters.
	* common/rsp-low.h (remote_escape_output): Add unit_size
	parameter and rename others. Update doc.
	* remote.c (align_for_efficient_write): New.
	(remote_write_bytes_aux): Add unit_size parameter and use it.
	Rename some variables.  Update doc.
	(remote_xfer_partial): Get unit size and use it.
	(remote_read_bytes_1): Add unit_size parameter and use it.
	Rename some variables. Update doc.
	(remote_write_bytes): Same.
	(remote_xfer_live_readonly_partial): Same.
	(remote_read_bytes): Same.
	(remote_flash_write): Update call to remote_write_bytes_aux.
	(remote_write_qxfer): Update call to remote_escape_output.
	(remote_search_memory): Same.
	(remote_hostio_pwrite): Same.

gdb/gdbserver/ChangeLog:

	* server.c (write_qxfer_response): Update call to
	remote_escape_output.