[PATCH] logic error in async event-top/gdb_readline2

[msnyder@sonic.net]

> OK, this function is the asynchronous version of top.c/gdb_readline
> (of which it is also a copy).  The main difference is that wherever
> the original (gdb_readline) returns a pointer to an input string,
> this versino (gdb_readline2) passes the pointer to a callback called
> 'input_handler'.
>
> And the problem is that the author neglected to make sure that
> gdb_readline2 also returns after calling the callback.
>
> As a result, we will enter code that was not ment to execute at
> this time, and will access a pointer to memory that has already
> been freed.

Committed.