HtmlParser: Update the list of available tags to the current HTML5 spec.
This adds <template>, <data>, and <main>, renames <command> to <menuitem>,
and moves around <article> and <u> to their current places in the list of
HTML elements.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51600162
HtmlParser: Add the stack of template insertion modes and some machinery for manipulating that.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51600185
HtmlParser: Add the IN_TEMPLATE insertion mode and a stub dispatch function
for it.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=51608008
Merge branch 'master' of https://github.com/google/gumbo-parser into moe_writing_branch_from_1fbc93bdf97dde6b07b67abb29a71d779f533dd8