PR remote/15455 - QTro remote packet broken

PR remote/15455 - QTro remote packet broken

In the function remote_trace_set_readonly_regions in gdb/remote.c, the
local variable 'offset' does not account for "QTro" at the start of
the packet with the result that if there are any read-only regions,
the packet is sent -- but without the "QTro" -- causing the remote
stub to report that the packet is unsupported:

  Sending packet: $:0000000000400200,(...),00000000004560a4#ab...Packet received:

vs the expected:

  Sending packet: $QTro:0000000000400200,(...),00000000004560a4#31...Packet received: OK

We don't see the problem when testing with GDBserver, as that supports
qXfer:trace-frame-info:read, meaning GDBserver never needs to read
from the read-only sections directly itself.  This commit adds a test
that explicitly disables qXfer:trace-frame-info:read.

gdb/
2013-05-10  David Taylor  <dtaylor@emc.com>

	PR remote/15455

	* remote.c (remote_trace_set_readonly_regions): Do not overwrite
	"QTro" at start of packet.

gdb/testsuite/
2013-05-10  Pedro Alves  <palves@redhat.com>

	PR remote/15455

	* gdb.trace/qtro.c: New file.
	* gdb.trace/qtro.exp: New file.