qSupported breaks RSP packet protocol

[tom . fowler]

This comment applies to gdb 6.7 built for an ARM ELF target on both
Linux and Windows(minGW).

Recent GDBs appear to contravene the RSP protocol by issuing the
"qSupported" command (from remote.c: remote_query_supported( )) before
the channel is initialized by remote_start_remote( ).

The effect is that the following sequence of bytes are emitted
immediately after connection:

->
$qSupported#37

<-
+$#00

->
++$Hc-1#09

i.e. There is a spurious second "+" ACK before the "Hc-1" command. In
previous versions there was no "qSupported" command, so
remote_start_remote( ) was the first writer to the RSP channel and the
first bytes written to the channel were:

->
+$Hc-1#09

<-
+$#00

->
+$qC#b4

...