I finally found the time to commit the changes to the hamburger menu discussed in this post:

<https://fossil-scm.org/forum/forumpost/2abe305c2d>

While at it, I have also updated the default skin to support customization of the hamburger menu through the header.txt file, and the sitemap is only loaded if the menu would otherwise be empty.

The check-ins are here:

<https://www.fossil-scm.org/index.html/timeline?&r=js-hamburger-menu>

(The work was scattered over multiple days, but the compact period of check-in time stamps is due to transferring the patches to the "live" repository in one go by scripting.)

As the changes only affect skin and documentation files (and not C source code files), they can be tested locally without rebuilding Fossil from source code: download the modified default skin files and launch a Fossil server with the `--skin` option (note: also requires at least one forward slash on Windows, i.e. `fossil ui --skin ./path\to\skin-files`).

I have performed careful tests, according to the template of the initial hamburger menu browser test matrix from this post:

<https://fossil-scm.org/forum/forumpost/7b08115de712a>

The patch to close the menu by ESC or by clicking outside was tested separately from the rest, and the customization feature was tested with various configurations. Current test results are as follows:

|:Browser |:Pass? |:Commentary |
--------------------------------
|:IE8 |:-- |:Not re-tested |
|:IE9 |:Partial |:The customized menu works, as `querySelector()` is not called; single-column layout |
|:IE10 |:Yes |:Somewhat unbridled column breaks with the customized menu |
|:IE11 |:Yes |: |
|:Edge |:Yes |: |
|:SM 2.25 |:-- |:Not tested |
|:SM 2.49.4 |:-- |:Not tested |
|:Firefox 12 |:-- |:Not tested |
|:Firefox 21esr |:-- |:Not tested |
|:Firefox 43esr |:-- |:Not tested |
|:Firefox 47esr |:-- |:Not tested |
|:Firefox 52esr |:-- |:Not tested |
|:Firefox 62 |:Yes |:Column breaks are also fixed |
|:Konqueror 5 |:Yes |: |
|:Safari |:-- |:No version of Safari tested, so far |
|:Chrome 49 |:Partial |:Single-column layout |
|:Chrome 71 |:Yes |: |

Comments and changes to code and documentation are welcome (content-related or of grammatical nature), as well as additions to the test results.

***

<small>The Markdown markup to reproduce and complete the test matrix can be extracted from the source code of this forum post, accessible through the [`/artifact`](https://www.fossil-scm.org/index.html/help?cmd=/artifact) web page (i.e. replace the `/forumpost` part of the URL of this forum post with `/artifact`):</small>

<small>`https://fossil-scm.org/forum/artifact/FORUM_POST_HASH`</small>