patch 9.0.1391: "clear" macros are not always used

Problem:    "clear" macros are not always used.
Solution:   Use ALLOC_ONE, VIM_CLEAR, CLEAR_POINTER and CLEAR_FIELD in more
            places. (Yegappan Lakshmanan, closes #12104)
diff --git a/src/fileio.c b/src/fileio.c
index 5a2e388..1966420 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -4382,7 +4382,7 @@
     // file, not reset the syntax highlighting, clear marks, diff status, etc.
     // Force the fileformat and encoding to be the same.
     if (reload_options)
-	memset(&ea, 0, sizeof(ea));
+	CLEAR_FIELD(ea);
     else
 	prepped = prep_exarg(&ea, buf);