Currently, all ".bat" entry points use "~dp0python" to ensure that the
Python that is used to execute the tool is the one in depot_tools. This
prevents any sort of system override.

Remove this override so that PATH solely determines which Python is
used. To accommodate users who invoked these tools without Python on the
PATH, we still still add "depot_tools" as a catch-all PATH suffix.

Some tools were also not using DOS-style line endings. This CL fixes
this.

BUG=chromium:714293, chromium:724902
TEST=None

Change-Id: I06e9583a668c767196a2a335547aded868f2a2b5
Reviewed-on: https://chromium-review.googlesource.com/517236
Commit-Queue: Daniel Jacques <dnj@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Marc-Antoine Ruel <maruel@chromium.org>