MAVLink: moved CRC table into program

this saves 256 bytes of memory

libraries/GCS_MAVLink/GCS_MAVLink.cpp

@@ -68,3 +68,10 @@ void comm_send_buffer(mavlink_channel_t chan, const uint8_t *buf, uint8_t len)
 	}
 }
 
+static const uint8_t mavlink_message_crc_progmem[256] PROGMEM = MAVLINK_MESSAGE_CRCS;
+
+// return CRC byte for a mavlink message ID
+uint8_t mavlink_get_message_crc(uint8_t msgid)
+{
+	return pgm_read_byte(&mavlink_message_crc_progmem[msgid]);
+}

libraries/GCS_MAVLink/GCS_MAVLink.h

@@ -15,6 +15,10 @@
 
 #define MAVLINK_SEND_UART_BYTES(chan, buf, len) comm_send_buffer(chan, buf, len)
 
+// define our own MAVLINK_MESSAGE_CRC() macro to allow it to be put
+// into progmem
+#define MAVLINK_MESSAGE_CRC(msgid) mavlink_get_message_crc(msgid)
+
 #if CONFIG_HAL_BOARD == HAL_BOARD_APM1 || CONFIG_HAL_BOARD == HAL_BOARD_APM2
 #include <util/crc16.h>
 #define HAVE_CRC_ACCUMULATE
@@ -146,4 +150,7 @@ uint8_t mavlink_check_target(uint8_t sysid, uint8_t compid);
 // return a MAVLink variable type given a AP_Param type
 uint8_t mav_var_type(enum ap_var_type t);
 
+// return CRC byte for a mavlink message ID
+uint8_t mavlink_get_message_crc(uint8_t msgid);
+
 #endif // GCS_MAVLink_h