Add third_party/pymox/src to .gitignore.
Add third_party/pymox/src to .gitignore.

BUG=none
TEST=ran "git status"
TBR=bradnelson

Review URL: http://codereview.chromium.org/8659023

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@111809 0039d316-1c4b-4281-b951-d872f2087c98

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