Modify licenses.py to handle Windows paths and support all DEPS....

Modify licenses.py to handle Windows paths and support all DEPS.
Also bring about_credits.html up to date.

1. licenses.py was failing on Windows because of path separators, so I 
   changed remaining path strings to use os.path.join.

2. I wasn't seeing all DEPS on my system, so I modified DEPS locally to 
   ignore os_deps. That led to several changes to make sure os-specific
   libraries (pdfsqueeze, GTM, for example) get attribution in about_credits.

3. Some of the code we pull in doesn't need attribution in our about_credits
   (windows SDK), so I added new ignore rules.

BUG=none
TEST= dunno. about:credits credits everything we include?
R= evan@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=71570

[evanm, 2011-01-16 18:26:27]

LGTM

http://codereview.chromium.org/6263006/diff/3001/tools/licenses.py
File tools/licenses.py (right):

http://codereview.chromium.org/6263006/diff/3001/tools/licenses.py#newcode67
tools/licenses.py:67: # ---- in DEPS.
Don't forget to follow up on this (I don't quite understand the comment) --
perhaps file a bug?

http://codereview.chromium.org/6263006/diff/3001/tools/licenses.py#newcode128
tools/licenses.py:128: # pdfsqueeze is Apache Licensed, reuse the same file from
GTM:
I'm not sure in this case, but some licenses require you include their
copyrights (which will list different authors, even when the body of the license
is the same).