patch 8.1.0770: inconsistent use of ELAPSED_FUNC

Problem:    Inconsistent use of ELAPSED_FUNC.
Solution:   Consistently use ELAPSED_FUNC.  Also turn ELAPSED_TYPE into a
            typedef. (Ozaki Kiichi, closes #3815)
diff --git a/src/misc1.c b/src/misc1.c
index 0a6dc87..a4b5628 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -3891,7 +3891,7 @@
 	{
 #ifdef ELAPSED_FUNC
 	    static int		did_init = FALSE;
-	    static ELAPSED_TYPE	start_tv;
+	    static elapsed_T	start_tv;
 
 	    /* Only beep once per half a second, otherwise a sequence of beeps
 	     * would freeze Vim. */