Implement multiple-filesystem support for remote targets

This commit allows GDB to access executables and shared libraries
on remote targets where the remote stub does not share a common
filesystem with the inferior(s).  A new packet "vFile:setfs" is
added to the remote protocol and the three remote hostio functions
with filename arguments are modified to send "vFile:setfs" packets
as necessary.

gdb/ChangeLog:

	* remote.c (struct remote_state) <fs_pid>: New field.
	(new_remote_state): Initialize the above.
	(PACKET_vFile_setfs): New enum value.
	(remote_hostio_set_filesystem): New function.
	(remote_hostio_open): Call the above.
	(remote_hostio_unlink): Likewise.
	(remote_hostio_readlink): Likewise.
	(_initialize_remote): Register new "set/show remote
	hostio-setfs-packet" command.
	* NEWS: Announce new vFile:setfs packet.

gdb/doc/ChangeLog:

	* gdb.texinfo (Remote Configuration): Document the
	"set/show remote hostio-setfs-packet" command.
	(Host I/O Packets): Document the vFile:setfs packet.

1 files changed, 6 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index a309dbf..23f20a7 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -174,6 +174,12 @@ qXfer:exec-file:read
   Return the full absolute name of the file that was executed to
   create a process running on the remote system.
 
+vFile:setfs:
+  Select the filesystem on which vFile: operations with filename
+  arguments will operate.  This is required for GDB to be able to
+  access files on remote targets where the remote stub does not
+  share a common filesystem with the inferior(s).
+
 fork stop reason
   Indicates that a fork system call was executed.