gdbserver: Handle 'v' packet while processing qSymbol.

gdbserver: Handle 'v' packet while processing qSymbol.

On powerpc64, qSymbol query may require gdb to read a function
descriptor, sending a vFile packet to gdbserver.  Thus, we need
to handle 'v' packet in look_up_one_symbol.

vFile replies may be quite long, and require reallocating own_buf.
Since handle_v_requests assumes the buffer is the static global own_buf
from server.c and reallocates it, we need to make own_buf global and
use it from look_up_one_symbol instead of using our own auto variable.
I've also done the same change in relocate_instruction, just in case.

On gdb side, in remote_check_symbols, rs->buf may be clobbered by vFile
handling, yet we need its contents for the reply (the symbol name is
stored there).  Allocate a new buffer instead.

This broke fast tracepoints on powerpc64, due to errors in reading IPA
symbols.

gdb/ChangeLog:

	* remote.c (remote_check_symbols): Allocate own buffer for reply.

gdbserver/ChangeLog:

	* remote-utils.c (look_up_one_symbol): Remove own_buf, handle 'v'
	packets.
	(relocate_instruction): Remove own_buf.
	* server.c (own_buf): Make global.
	(handle_v_requests): Make global.
	* server.h (own_buf): New declaration.
	(handle_v_requests): New prototype.