use true/false instead of 1/0 detected and changed by clang-tidy

src/balance.cpp

@@ -930,7 +930,7 @@ int Balance::shift()
         // else add split I-1 or J+1 to set and try again
         // delta = size of expanded split set that will satisy criterion
 
-        while (1) {
+        while (true) {
           delta = (j-i) * close;
           midpt = 0.5 * (split[i]+split[j]);
           start = midpt - 0.5*delta;