[Bug preprocessor/65852] Incorrect escaping in depfiles

[paul_robinson at playstation dot sony.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65852

--- Comment #10 from Paul Robinson <paul_robinson at playstation dot sony.com> ---
I thought I had heard your name before!  Howdy...

Granted this is an obscure corner case, but they are legal filenames,
using a leading # is less horrifying than a leading space, and the
depfile that gcc produces is demonstrably wrong.

I just downloaded Cygwin with gcc 4.9.2 to my Windows, and the behavior
is exactly the same (using \ instead of / as the separator, seeing \\\ 
before the space and only \\ before the #).

Anyway, can we agree that the inconsistent handling of space and # is
a bug?  You can set the priority as low as you like.

FYI, you do _not_ want to escape all backslashes; that will break
BSD Make, which doesn't do any quoting at all.