Substitute '\' with '\\' in extended-prompt

[Yao Qi]

Phil Muldoon <pmuldoon@redhat.com> writes:

> However I have not looked at it in detail yet, but that is my first
> guess. If you remove it, do the Python prompt tests fail?  I'll do

I remove it, and no python tests fail.  The output of
"set extended-prompt \w" changed from
"\\\\build2-lucid-cs\\yqi\\yqi\\arm-none-eabi" to
"\\build2-lucid-cs\yqi\yqi\arm-none-eabi".  I did the test on mingw32
host.

> some archaeology and try to find out why today.  However, if it is
> blocking your work, and without the substitution all the tests still
> pass, then I would suggest we remove it for now.  We can always add it
> back, and the next release of GDB is not terribly soon.

I am in no hurry.  I can post a patch to remove it if we don't have any
clues in three days.

-- 
Yao (齐尧)