patch 8.1.1414: alloc() returning "char_u *" causes a lot of type casts

Problem:    Alloc() returning "char_u *" causes a lot of type casts.
Solution:   Have it return "void *". (Mike Williams)  Define ALLOC_ONE() to
            check the simple allocations.
diff --git a/src/blowfish.c b/src/blowfish.c
index ce49957..65f8932 100644
--- a/src/blowfish.c
+++ b/src/blowfish.c
@@ -645,7 +645,7 @@
     char_u*		seed,
     int			seed_len)
 {
-    bf_state_T	*bfs = (bf_state_T *)alloc_clear(sizeof(bf_state_T));
+    bf_state_T	*bfs = ALLOC_CLEAR_ONE(bf_state_T);
 
     if (bfs == NULL)
 	return FAIL;