GDBRemoteCommunication::DecompressPacket assumed that the buffer it was

working with (the Communication m_bytes ivar) contained a single packet.
Instead, it may contain multitudes.  Find the boundaries of the first packet
in the buffer and replace that with the decompressed version leaving the
rest of the buffer unmodified.
<rdar://problem/21841377> 

llvm-svn: 243846