Move the traceframe_available_memory code from memory_xfer_partial_1 down to the targets

As a follow-up to

  [PATCH 7/8] Adjust read_value_memory to use to_xfer_partial
  https://sourceware.org/ml/gdb-patches/2014-02/msg00384.html

this patch moves traceframe_available_memory down to the target side.
After this patch, the gdb core code is cleaner, and code on handling
unavailable memory is moved to remote/tfile/ctf targets.

In details, this patch moves traceframe_available_memory code from
memory_xfer_partial_1 to remote target only, so remote target still
uses traceframe_info mechanism to check unavailable memory, and use
remote_ops to read them from read-only sections.  We don't use
traceframe_info mechanism for tfile and ctf target, because it is
fast to iterate all traceframes from trace file, so the summary
information got from traceframe_info is not necessary.

This patch also moves two functions to remote.c from target.c,
because they are only used in remote.c.  I'll clean them up in another
patch.

gdb:

2014-03-22  Yao Qi  <yao@codesourcery.com>

	* ctf.c (ctf_xfer_partial): Check the return value of
	exec_read_partial_read_only, if it is not TARGET_XFER_OK,
	return TARGET_XFER_UNAVAILABLE.
	* tracefile-tfile.c (tfile_xfer_partial): Likewise.
	* target.c (target_read_live_memory): Move it to remote.c.
	(memory_xfer_live_readonly_partial): Likewise.
	(memory_xfer_partial_1): Move some code to remote_read_bytes.
	* remote.c (target_read_live_memory): Moved from target.c.
	(memory_xfer_live_readonly_partial): Likewise.
	(remote_read_bytes): New, factored out from
	memory_xfer_partial_1.
Factor remote_read_bytes.

This patch moves code in remote_read_bytes on reading from the remote
stub to a new function remote_read_bytes_1.

gdb:

2014-03-22  Yao Qi  <yao@codesourcery.com>

	* remote.c (remote_read_bytes): Move code on reading from the
	remote stub to ...
	(remote_read_bytes_1): ... here.  New function.
Remove target_read_live_memory

As we move code on reading unavailable memory to target side, GDB core
side doesn't need the "switching momentarily out of tfind mode" dance.
The target remote knows how to read live memory (through remote_ops).

Remove set_traceframe_number and
make_cleanup_restore_traceframe_number, since they are no longer used.

gdb:

2014-03-22  Yao Qi  <yao@codesourcery.com>

	* remote.c (target_read_live_memory): Remove.
	(memory_xfer_live_readonly_partial): Rename it to
	remote_xfer_live_readonly_partial.  Remove argument 'object'.
	All callers updated.  Call remote_read_bytes_1
	instead of target_read_live_memory.
	* tracepoint.c (set_traceframe_number): Remove.
	(make_cleanup_restore_traceframe_number): Likewise .
	* tracepoint.h (set_traceframe_number): Remove declaration.
	(make_cleanup_restore_traceframe_number): Likewise.