Add Doxygen comments for PDALDimType struct

Author: jimmysoda

source/pdal/capi/Forward.h

@@ -44,11 +44,19 @@ namespace pdal
 
 typedef struct PDALDimType PDALDimType;
 
+/// A dimension type
 struct PDALDimType
 {
+	/// The dimension's identifier
 	uint32_t id;
+
+	/// The dimension's interpretation type
 	uint32_t type;
+
+	/// The dimension's scaling factor
 	double scale;
+
+	/// The dimension's offset value
 	double offset;
 };