less squares 4 speed + fixed some bugs (but found more)

LibSidServo/main.h

@@ -29,6 +29,16 @@
 extern conf_t Conf;
 double nanotime();
 void getModData(mountdata_t *mountdata);
+typedef struct{
+    double *x, *t, *t2, *xt; // arrays of coord/time and multiply
+    double xsum, tsum, t2sum, xtsum; // sums of coord/time and their multiply
+    size_t idx; // index of current data in array
+    size_t arraysz; // size of arrays
+} less_square_t;
+
+less_square_t *LS_init(size_t Ndata);
+void LS_delete(less_square_t **ls);
+double LS_calc_slope(less_square_t *l, double x, double t);
 
 // unused arguments of functions
 #define _U_         __attribute__((__unused__))