Toggle logging of transaction between Emacs and Gdb.
The log is stored in `gdb-debug-log' as an alist with elements
whose cons is send, send-item or recv and whose cdr is the string
being transferred. This list may grow up to a size of
`gdb-debug-log-max' after which the oldest element (at the end of
the list) is deleted every time a new one is added (at the front). (fn &optional ARG)
Non-nil if Gdb-Enable-Debug mode is enabled.
See the command `gdb-enable-debug' for a description of this minor mode.