Fix build failure on darwin due to darwin_read_dyld_info not being defined.

gdb/ChangeLog:

        * darwin-nat.c: Fix typo in TASK_DYLD_INFO_COUNT macro test
        used to decide whether to define darwin_read_dyld_info or not.
Delete unused variable in lynx_resume

gdb/gdbserver/ChangeLog:

        * lynx-low.c (lynx_resume): Delete variable ret.
LynxOS: Resume the same thread when receiving a thread create/exit event.

Before this patch, the ptid passed to lynx_resume was completely
ignored, and we used the current_inferior. This resulted in trying
to resume the inferior execution using the wrong ptid after having
received a thread create/exit event, because the inferior_ptid
was still set to the ptid prior to receiving the signal.

gdb/gdbserver/ChangeLog:

        * lynx-low.c (lynx_resume): Use the resume_info parameter
        to determine the ptid for the lynx_ptrace call, unless
        it is equal to minus_one_ptid, in which case we use the
        ptid of the current_inferior.
        (lynx_wait_1): After having received a thread create/exit
        event, resume the inferior's execution using the signaling
        thread's ptid, rather than the old ptid.
Allow powerpc-*-lynxos* GDBserver to send register map via XML...

... back to GDB.  The transfer occurs when GDB sends the
'qXfer:features:read:target.xml' packet.  This allows us to make
sure that GDB and GDBserver use the same register numbering.
This is important on Lynx 178, where GDB selects the rs6000:6000
architecture by default instead of the powerpc:common architecture.

gdb/gdbserver/ChangeLog:

        * configure.srv (powerpc-*-lynxos*): Set srv_xmlfiles.
Make x86-lynx GDBserver pass XML register map to GDB.

This is not strictly needed, since both GDB and GDBserver seem
to agree on the register numbering without this.  But this allows
us to make sure that this is always going to be the case.

gdb/gdbserver/ChangeLog:

        * configure.srv (i[34567]86-*-lynxos*): Set srv_xmlfiles.
Add ptrace error handling in lynx_resume

gdb/gdbserver/ChangeLog:

        * lynx-low.c (lynx_resume): Call perror_with_name if lynx_ptrace
        sets errno.
Simplifly ptrace_request_to_str's implementation...

... following Pedro's advice of using a temporary macro.

gdb/gdbserver/ChangeLog:

        * lynx-low.c (ptrace_request_to_str): Define a temporary
        macro and use it to simplify this function's implementation.