Translate ENOMEM to ERRCODE_OUT_OF_MEMORY in errcode_for_file_access().

Previously you got ERRCODE_INTERNAL_ERROR, which seems inappropriate,
especially given that we're trying to avoid emitting that in reachable
cases.

Alexander Kuzmenkov

Discussion: https://postgr.es/m/CALzhyqzgQph0BY8-hFRRGdHhF8CoqmmDHW9S=hMZ-HMzLxRqDQ@mail.gmail.com

src/backend/utils/error/elog.c

@@ -760,6 +760,10 @@ errcode_for_file_access(void)
 			edata->sqlerrcode = ERRCODE_DISK_FULL;
 			break;
 
+		case ENOMEM:			/* Out of memory */
+			edata->sqlerrcode = ERRCODE_OUT_OF_MEMORY;
+			break;
+
 		case ENFILE:			/* File table overflow */
 		case EMFILE:			/* Too many open files */
 			edata->sqlerrcode = ERRCODE_INSUFFICIENT_RESOURCES;