40306 with doc tweaks: Change behaviour expanding alias in () function definition.

Now an error unless the () is part of the same error as the name.
Add ALIAS_FUNC_DEF option to allow it again.

Src/input.c

@@ -670,3 +670,30 @@ ingetptr(void)
 {
     return inbufptr;
 }
+
+/*
+ * Check if the current input line, including continuations, is
+ * expanding an alias.  This does not detect alias expansions that
+ * have been fully processed and popped from the input stack.
+ * If there is an alias, the most recently expanded is returned,
+ * else NULL.
+ */
+
+/**/
+char *input_hasalias(void)
+{
+    int flags = inbufflags;
+    struct instacks *instackptr = instacktop;
+
+    for (;;)
+    {
+	if (!(flags & INP_CONT))
+	    break;
+	instackptr--;
+	if (instackptr->alias)
+	    return instackptr->alias->node.nam;
+	flags = instackptr->flags;
+    }
+
+    return NULL;
+}