encoding: move case-related utils up
This will be useful for the next commit that needs this code earlier.
Differential Revision: https://phab.mercurial-scm.org/D11024
changeset: {node}
revision: {rev}
user: {author}
date: {date|rfc822date}
summary: {desc}
{branches%branchname}{tags%tagname}{bookmarks%bookmarkname}