Use pv_error() instead of writing directly to stderr.

src/pv/elapsedtime.c

@@ -25,10 +25,9 @@
  */
 void pv_elapsedtime_read(struct timespec *return_time)
 {
-	/* TODO: use pv_error() rather than fprintf(). */
 	/*@-unrecog@ *//* splint doesn't know clock_gettime. */
 	if (0 != clock_gettime(CLOCK_MONOTONIC, return_time)) {
-		fprintf(stderr, "%s: %s: %s\n", PACKAGE_NAME, "clock_gettime", strerror(errno));
+		pv_error("%s: %s", "clock_gettime", strerror(errno));
 		/*@-exitarg@ *//* The special exit status is explicitly chosen. */
 		exit(PV_ERROREXIT_TRANSFER);
 		/*@+exitarg@ */