Have CanonicalizePath handle \ on Windows

Have CanonicalizePath handle \ on Windows. It's slightly slower to do so, so compensate for that by improving ReadFile to not use text mode (which is a bit slower), and then fixing the lexer to accept \r (it was previously relying on reading files in text mode to remove '\r's).

Timings:

before patch:
qpc: 1229494us
qpc: 1232420us
qpc: 1232493us
qpc: 1235035us
qpc: 1239521us
qpc: 1247100us
avg = 1234867us

with canon of \, fixing parser to accept \r and speedier ReadFile
qpc: 1196304us
qpc: 1200643us
qpc: 1187478us
qpc: 1190062us
qpc: 1182991us
qpc: 1203037us
avg = 1190128us

It would canonicalize "a bit". If a header was something like

a\b\..\d/../e.h

it'd end up as

a\b\..\e.h

(or something along those lines)

On Thu, Oct 30, 2014 at 2:57 PM, Nico Weber <notifications@github.com>
wrote:

> In src/includes_normalize-win32.cc:
>
> >    string err;
> > -  if (!CanonicalizePath(copy, &len, &err)) {
>
> Did this just do nothing previously, as it passed '\'s here?
>
> —
> Reply to this email directly or view it on GitHub
> <https://github.com/martine/ninja/pull/839/files#r19639297>.
>