Add missing header files.

These headers files were missing from the header files that
I added them to; the fact that they were missing didn't
lead to compile errors because by coincidence the missing
headers are included in the source files before including
these headers. But, after the reordering of header inclusions
by Tools/fix_headers.sh, these cases will give rise to compiler
errors.

src/lib/mathlib/math/Matrix.hpp

@@ -46,6 +46,8 @@
 #include <stdio.h>
 #include <cmath>
 
+#include "Vector.hpp"	// Vector and eigen_matrix_instance
+
 #include "matrix/math.hpp"
 #include <platforms/px4_defines.h>