Fix allocations and compiler warnings in ZROTG (#4289)

* Clean up ZROTG

Author: martin-frbg

interface/zrotg.c

@@ -30,14 +30,12 @@ void CNAME(void *VDA, void *VDB, FLOAT *C, void *VS) {
   FLOAT db_r = *(DB+0);
   FLOAT db_i = *(DB+1);
   //long double r;
-  FLOAT *r, *S1=(FLOAT *)malloc(2*sizeof(FLOAT));
-  FLOAT *R=(FLOAT *)malloc(2*sizeof(FLOAT));
+  FLOAT S1[2];
+  FLOAT R[2];
   long double d;
 
   FLOAT ada =  da_r * da_r + da_i * da_i; 
   FLOAT adb =  db_r * db_r + db_i * db_i; 
-  FLOAT adart = sqrt( da_r * da_r + da_i * da_i); 
-  FLOAT adbrt = sqrt( db_r * db_r + db_i * db_i); 
 
   PRINT_DEBUG_NAME;
 
@@ -115,10 +113,13 @@ void CNAME(void *VDA, void *VDB, FLOAT *C, void *VS) {
 			}
 	    	    } else {
 		        *C = ada / adahsq;
-		        if (*C >= safmin) 
+		        if (*C >= safmin) {
 			    *R = *DA / *C;
-		        else
+			    *(R+1) = *(DA+1) / *(C+1);
+			} else {
 			    *R = *DA * (h / adahsq);
+			    *(R+1) = *(DA+1) * (h / adahsq);
+			}
 		        *S = *S1 * ada / adahsq;
 		    	*(S+1) = *(S1+1) * ada / adahsq;
 		    }
@@ -178,4 +179,4 @@ void CNAME(void *VDA, void *VDB, FLOAT *C, void *VS) {
 		}
 	}
 }
-	
+