Delegate to target_ops->beneath for TARGET_OBJECT_RAW_MEMORY

GDB on x86_64-linux is unable to disassemble on core-file target.

$ ./gdb ./testsuite/gdb.base/corefile
(gdb) core-file ./testsuite/gdb.base/corefile.core
(gdb) disassemble main
Dump of assembler code for function main:
   0x0000000000400976 <+0>:	Cannot access memory at address 0x400976

However, it works if we turn code-cache off.

(gdb) set code-cache off
(gdb) disassemble main,+4
Dump of assembler code from 0x400976 to 0x40097a:
   0x0000000000400976 <main+0>:	push   %rbp
   0x0000000000400977 <main+1>:	mov    %rsp,%rbp
End of assembler dump.

When code-cache is off, GDB will iterate target_ops from top to bottom
and call to_xfer_partial.  When current_target is "core", it will call
to_xfer_partial of target "exec", which reads the contents for
disassemble.  However, dcache uses TARGET_OBJECT_RAW_MEMORY to read,
but target_xfer_partial doesn't delegate requests to beneath for
TARGET_OBJECT_RAW_MEMORY.

This patch factors out the iteration from top to bottom to a new
function, raw_memory_xfer_partial, and use it for
TARGET_OBJECT_RAW_MEMORY.

Regression tested on x86_64-linux.

gdb:

2013-11-29  Yao Qi  <yao@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	* dcache.c (dcache_read_line): Use current_target.beneath
	instead of &current_target.
	* target.c (memory_xfer_partial_1): Factor code out to ...
	(raw_memory_xfer_partial): ... it.  New function.
	(target_xfer_partial): Call raw_memory_xfer_partial if OBJECT
	is TARGET_OBJECT_RAW_MEMORY.
Plug target side conditions and commands leaks.

The memory management of bp_location->target_info.conditions|tcommands
is currently a little fragile.  If the target reports support for
target conditions or commands, and then target side breakpoint support
is disabled, or some error is thrown before remote_add_target_side_XXX
is called, we'll leak these lists.  This patch makes us free these
lists when the locations are deleted, and also, just before recreating
the commands|conditions lists.

Tested on x86_64 Fedora 17, native and gdbserver.

gdb/
2013-11-29  Pedro Alves  <palves@redhat.com>

	* breakpoint.c (build_target_condition_list): Release previous
	conditions.
	(build_target_command_list): Release previous commands.
	(bp_location_dtor): Release target conditions and commands.
	* remote.c (remote_add_target_side_condition): Don't release
	conditions.
	(remote_add_target_side_commands): Don't release commands.
UNWIND_NULL_ID is no longer used anywhere.  Update comments.

Unfortunately, UNWIND_NULL_ID is exported to Python as
gdb.FRAME_UNWIND_NULL_ID so we can't really eliminate it.

(I'd assume scripts just check the result of Frame.unwind_stop_reason,
and compare it to gdb.FRAME_UNWIND_NO_REASON.  That at most, they'll
pass the result of Frame.unwind_stop_reason to
gdb.frame_stop_reason_string.  I'd prefer to just get rid of it, but
because we make an API promise, we get to keep this around for
compatibility, in case a script does refer to gdb.FRAME_UNWIND_NULL_ID
directly.)

gdb/
2013-11-29  Pedro Alves  <palves@redhat.com>

	* unwind_stop_reasons.def (UNWIND_NULL_ID): Update comment.

gdb/doc/
2013-11-29  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (Frames In Python) <gdb.FRAME_UNWIND_NULL_ID>:
	Update comment.