Bug 1006812: Use mozilla::pkix::der to decode the key usage extension, r=keeler, a=sledru

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extra : rebase_source : cc40c641f15602e7008c90c4c50730e4ad2b38fe
extra : source : 2572716c3646aa70b0109e602ee5113c6ad17138
Bug 1031542: Add test case for key usage without any value bits, r=keeler, a=test-only

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extra : rebase_source : ff6f311389388900c0c56868a880d9e6a479c533
extra : source : 25bdc0db6b042fe6fbba61b80cb8a4ac7cb588eb