Added PG 10 compatibility wrapper to simple_prompt()

Also checking for malloc failure into previous version's simple_prompt()
calls.

bin/pgut/pgut.c

@@ -434,7 +434,26 @@ simple_string_list_size(SimpleStringList list)
 static char *
 prompt_for_password(void)
 {
-	return simple_prompt("Password: ", 100, false);
+	char *buf;
+#define BUFSIZE 100
+
+#if PG_VERSION_NUM < 100000
+	buf = simple_prompt("Password: ", BUFSIZE, false);
+#else
+	buf = (char *)malloc(BUFSIZE);
+	if (buf != NULL)
+		simple_prompt("Password: ", buf, BUFSIZE, false);
+#endif
+
+	if (buf == NULL)
+		ereport(FATAL,
+			(errcode_errno(),
+			 errmsg("could not allocate memory (" UINT64_FORMAT " bytes): ",
+				(unsigned long) BUFSIZE)));
+
+	return buf;
+
+#undef BUFSIZE
 }