Fix code tags that contain html encoded characters, and fix at links.

docs/html/about/versions/android-1.6.jd

docs/html/about/versions/android-4.0.3.jd

docs/html/about/versions/android-4.0.jd

docs/html/about/versions/android-4.2.jd

docs/html/about/versions/android-4.3.jd

docs/html/about/versions/marshmallow/android-6.0-changes.jd

docs/html/about/versions/marshmallow/android-6.0.jd

docs/html/google/play/billing/billing_integrate.jd

docs/html/google/play/expansion-files.jd

docs/html/google/play/licensing/setting-up.jd

docs/html/guide/components/activities.jd

docs/html/guide/practices/compatibility.jd

docs/html/guide/topics/connectivity/bluetooth.jd

docs/html/guide/topics/connectivity/wifip2p.jd

docs/html/guide/topics/manifest/meta-data-element.jd

docs/html/guide/topics/manifest/uses-feature-element.jd

docs/html/guide/topics/providers/calendar-provider.jd

docs/html/guide/topics/providers/contacts-provider.jd

docs/html/guide/topics/renderscript/compute.jd

docs/html/guide/topics/search/search-dialog.jd