reposcan: avoid infinite recursion - don't follow symlinks when scanning

The whole reposcan mechanism is a mess and should be rewritten ...

changeset: hack to "reload" page to make #target links work first time

Like 9dfd9d242728 did for pull requests.

files: fix hiding of old content while reloading

Fixing typo from 43cafe348c9a.

diff view: improve appearance of line numbers

* display the ellipsis just once and centered
instead of showing in twice in both - and + columns
* expand column width as needed to accomodate longer numbers
(previously, the column width was fixed)
* enable box-sizing: border-box for the number links to
make it easier to set paddings

comments: remove line breaks after user mentions in comment previews

Previously, the preview might look like this:

@username

, have you seen it?

Now it should look like this:

@username, have you seen it?

rst: in @mention parser, escape spaces so they don't go to HTML

This eliminates extra spaces around @mentions. Every time mention was followed
by a comma, for example:

@username, have you seen it?

it turned into:

@username , have you seen it?

So an extra space was inserted. It was inserted because otherwise rst parser
might not recognise the markup (i.e. @user1,@user2 is replaced by
**user1**,**user2** — that would be interpreted as <b>user1**,**user2</b>).

See http://docutils.sf.net/docs/ref/rst/restructuredtext.html#character-level-inline-markup

diff view: do not hide overflow on very long lines that cannot be wrapped

When a change contains very long lines that cannot be wrapped because they
contain very long 'words' without spaces, the overflow is currently not
visible at all. This occurrence of such very long non-wrappable words is
pretty uncommon, but can for example happen in comma-separated value files.

Not touching the existing behavior of trying to wrap long lines, this patch
adds horizontal scrollbars for these exceptional cases of unavoidable
overflow.
On normal lines and long lines that can be wrapped, the diff block remains
the same as before.

templates: only bind pager event handlers once - avoid "leaks" and repeated page loads

Summary page ended up hammering the server and when pages were loaded one time
extra for each paging click.

Just moving javascript code from the data template (where it would be re-run on
each paging) and to the main page template.

pullrequest overview: fix 'my pullrequests' overview

Commit bd4f453a0055 fixed the pager links on pullrequest overviews, but
broke the 'my pull requests' page due to insufficient testing and
incomplete Python understanding.

pullrequest overview: fix missing pager links

Commit 0f9a48e0adc3 refactored the pullrequest overview pages, but has a
bug causing no more than 10 pull requests to be shown, without pager links.
The code assumed that 'pager' was a variable, rather than a method, of the
pullrequests structure.

setup: bump mercurial requirement to 2.9

Commit 1cd9bdf1362d started using iterbranches() method of branchmap

security: Fix HTML and JavaScript injection.

This fixes CVE-2015-1864