add function for logarithmus to base 10 for convenience

src/logarithmus.c

@@ -11,6 +11,10 @@ double logX(double b, double a){
     return(logN(a, 0.000001)/logN(b, 0.000001));
 }
 
+double logDec(double a){
+    return logX(10.0, a);
+}
+
 double logN(double x, double eps){
     if(x <= 0){
         return -1.0;