Add preliminary support for HMC5883L magnetometer and MPL3115A2 altimeter.

Logging only, at this stage.

matrix.c

@@ -19,6 +19,7 @@ void matrix_multiply(float *dest, float *m1, float *m2, int r, int c, int n)
 	}
 }
 
+#if 0
 /* dest[r][c] = m1[r][n] * m2[c][n] */
 void matrix_multiply_t(float *dest, float *m1, float *m2, int r, int c, int n)
 {
@@ -33,6 +34,7 @@ void matrix_multiply_t(float *dest, float *m1, float *m2, int r, int c, int n)
 		}
 	}
 }
+#endif
 
 /* dest[r][c] = m1[r][c] + m2[r][c] */
 void matrix_add(float *dest, float *m1, float *m2, int r, int c)
@@ -64,6 +66,7 @@ void dump_matrix(float *m, int r, int c)
 }
 #endif
 
+#if 0
 /* Invert src into dst.
  * NOTE: destroys the src matrix
  */
@@ -145,3 +148,4 @@ void matrix_invert(float *dst, float *src, int size)
 
 	/* src should now be the identiy matrix while dst holds the answer */
 }
+#endif