+/** @brief Reallocate memory
+ * @param ptr Block to reallocated
+ * @param n Bytes to allocate
+ * @return Pointer to allocated memory
+ *
+ * Terminates the processf on error. It is NOT guaranteed that any
+ * additional memory allocated is 0-filled. The block must have been
+ * allocated with xmalloc_noptr() (or xrealloc_noptr()) initially.
+ */