bug#22984: 25.0.92; Typo in etc/DEBUG

[N. Jackson]

In line 75 of etc/DEBUG there is the following text:

  you can start GDB by typing "M-x GDB RET"

IIUC, this should say

  you can start GDB by typing "M-x gdb RET"

Additionally, it might be helpful if this file mentioned the "debugger"
that pops up when debug-on-error is non-nil. This "debugger" doesn't
seem to be a debugger at all, but just a help window with a backtrace in
it. If it is a debugger, then perhaps etc/DEBUG should say how to use
it, and if it isn't, then perhaps etc/DEBUG should say so?

Also, can one use `M-x gdb RET' in the same instance of Emacs that one
wishes to debug? I can think of good reasons why this might not work, so
I almost expect that it doesn't, but, on the other hand, it would be
convenient if it did work. So perhaps etc/DEBUG should explicitly say
that it can or cannot be done?

Thanks.

N.