Fix variable names in WireProtocol_Receiver.c

[nfbot]

From nf-interpreter created by cw2 : nanoframework/nf-interpreter#59

uint8_t m_receptionBuffer[256]; // was 2048
uint32_t m_lastPacketSequence;
uint8_t* m_szMarker;
WP_Message m_inboundMessage;
uint16_t m_lastOutboundMessage;

m_ prefix is used for members, static variables should have s_ (file scope) or g_ (global). Alternatively, don't use any prefix.