Support more of mathlib function for easier swap in px4.

test/matrixAssignment.cpp

@@ -9,6 +9,7 @@ int main()
 {
     Matrix3f m;
     m.setZero();
+    m.zero();
     m(0, 0) = 1;
     m(0, 1) = 2;
     m(0, 2) = 3;
@@ -26,6 +27,15 @@ int main()
         TEST(fabs(data[i] - m2.data()[i]) < 1e-6f);
     }
 
+    float data2d[3][3] = {
+        {1, 2, 3},
+        {4, 5, 6},
+        {7, 8, 9}};
+    m2 = Matrix3f(data2d);
+    for(int i=0; i<9; i++) {
+        TEST(fabs(data[i] - m2.data()[i]) < 1e-6f);
+    }
+
     float data_times_2[9] = {2, 4, 6, 8, 10, 12, 14, 16, 18};
     Matrix3f m3(data_times_2);