Replace -1 with TARGET_XFER_E_IO

Hi,
This patch replaces -1 with TARGET_XFER_E_IO in the implementations of
to_xfer_partial and their callees.  This change is quite mechanical,
and makes the next patch shorter.

gdb:

2014-02-07  Yao Qi  <yao@codesourcery.com>

	* auxv.c (procfs_xfer_auxv): Replace -1 with TARGET_XFER_E_IO.
	(ld_so_xfer_auxv): Likewise.
	* bfd-target.c (target_bfd_xfer_partial): Likewise.
	* bsd-kvm.c (bsd_kvm_xfer_partial): Likewise.
	* corelow.c (core_xfer_partial): Likewise.
	* ctf.c (ctf_xfer_partial): Likewise.
	* darwin-nat.c (darwin_read_dyld_info): Likewise.
	(darwin_xfer_partial): Likewise.
	* exec.c (exec_xfer_partial): Likewise.
	* gnu-nat.c (gnu_xfer_partial): Likewise.
	* ia64-hpux-nat.c (ia64_hpux_xfer_uregs): Likewise.
	* inf-ptrace.c (inf_ptrace_xfer_partial): Likewise.
	* inf-ttrace.c (inf_ttrace_xfer_partial): Likewise.
	* linux-nat.c (linux_xfer_siginfo): Likewise.
	(linux_proc_xfer_spu): Likewise.
	* procfs.c (procfs_xfer_partial): Likewise.
	* record-full.c (record_full_xfer_partial): Likewise.
	(record_full_core_xfer_partial): Likewise.
	* remote-sim.c (gdbsim_xfer_partial): Likewise.
	* remote.c (remote_write_qxfer): Likewise.
	(remote_write_qxfer, remote_read_qxfer): Likewise.
	(remote_xfer_partial): Likewise.
	* rs6000-nat.c (rs6000_xfer_partial): Likewise.
	(rs6000_xfer_shared_libraries): Likewise.
	* sparc-nat.c (sparc_xfer_wcookie): Likewise.
	* spu-linux-nat.c (spu_proc_xfer_spu): Likewise.
	(spu_xfer_partial): Likewise.
	* target.c (memory_xfer_partial_1): Likewise.
	* tracepoint.c (tfile_xfer_partial): Likewise.
	* windows-nat.c (windows_xfer_shared_libraries): Likewise.
	(windows_xfer_partial): Likewise.

gdb/ctf.c

@@ -1493,7 +1493,7 @@ ctf_xfer_partial (struct target_ops *ops, enum target_object object,
     }
 
   /* Indicate failure to find the requested memory block.  */
-  return -1;
+  return TARGET_XFER_E_IO;
 }
 
 /* This is the implementation of target_ops method