patch 7.4.1073
Problem:    Alloc_id depends on numbers, may use the same one twice.  It's not
            clear from the number what it's for.
Solution:   Use an enum.  Add a function to lookup the enum value from the
            name.
diff --git a/src/globals.h b/src/globals.h
index 54a1d72..0931466 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -1621,7 +1621,7 @@
 
 #ifdef FEAT_EVAL
 /* set by alloc_fail(): ID */
-EXTERN int  alloc_fail_id INIT(= 0);
+EXTERN alloc_id_T  alloc_fail_id INIT(= aid_none);
 /* set by alloc_fail(), when zero alloc() returns NULL */
 EXTERN int  alloc_fail_countdown INIT(= -1);
 /* set by alloc_fail(), number of times alloc() returns NULL */