Added push_back_multiple, free, and remove to DArray. Added tests.

tests/cmocka/main.c

@@ -1,11 +1,19 @@
 #include <cmocka.h>
 
 int DString_tests_run(void);
+int DArray_tests_run(void);
 
 int main(void) {
     int failed = 0;
 
     failed = DString_tests_run();
+    if (failed) {
+        return failed;
+    }
+    failed = DArray_tests_run();
+    if (failed) {
+        return failed;
+    }
 
     return failed;
 }