gentlsrc: add support for FLIR Spinnaker cameras

This also required changing how we read values, as FLIR uses little
endian. Timestamps are handled differently as well.

We're even more overdue for moving to properly parse the XML, just a
matter of if we'll use the GenApi reference implementation or something
else like Aravis.

sys/gentl/gstgentlsrc.h

@@ -45,6 +45,7 @@ struct _GstGenTlProducer
 {
   gchar* cti_path;
   guint32 acquisition_mode_value;
+  guint32 timestamp_control_latch_value;
 
   guint64 width;
   guint64 height;
@@ -55,9 +56,11 @@ struct _GstGenTlProducer
   guint64 acquisition_stop;
   guint64 tick_frequency_low;
   guint64 tick_frequency_high;
-  guint64 timestamp_control_latch;
-  guint64 timestamp_low;
-  guint64 timestamp_high;
+  guint64 timestamp_control_latch;  // GevTimestampControlLatch
+  guint64 timestamp;                // TimestampLatchValue
+  guint64 timestamp_low;            // GevTimestampValueLow
+  guint64 timestamp_high;           // GevTimestampValueHigh
+  guint16 port_endianness;
 };
 
 
@@ -71,6 +74,7 @@ struct _GstGenTlProducer
 typedef enum {
   GST_GENTLSRC_PRODUCER_BASLER,
   GST_GENTLSRC_PRODUCER_EVT,
+  GST_GENTLSRC_PRODUCER_FLIR,
 } GstGenTlSrcProducer;