add explicit dependency on minimal font packages for all linux targets

This is required in a minimal headless setup where the font packages
are not likely to be installed by default, see #1961.
fix wrong comparison when parsing list parameters

Fixes #1906
fix various compilation warnings

Mostly taken from the changes in #1849
[breaking change] update to the latest Qt to fix multiple issues

fixes #2055 via wkhtmltopdf/qt@31de8043c2334a81c96df5c56c31c73396cd5394
fixes #1640 via wkhtmltopdf/qt@e5bcc99edbc87c45bb80dc3c8e7360431f090d16

The thead/tfoot repeating logic is still enabled by default and can be
turned off for a specific table or all tables via CSS:

thead, tfoot { display: table-row-group }

The table row page-break logic is now disabled by default. You will have
to enable it for specific rows or for all tables via CSS:

tr { page-break-inside: avoid }

You will need to change your CSS or use the --user-style-sheet option
to pass a custom style sheet to the conversion process.
Fix unicode URLs

Store in hashmap strings parsed from percent-encoded unicode URLs.
Patch fixes behaviour of wkhtmltopdf with percent-encoded urls.
They are gathered from body as unicode strings but are read from
argument list as percent-encoded strings.
add option --dump-render-tree for viewing the WebKit render tree

This can be useful for understanding the structure of the input HTML
and seeing how it translates into the browser's render tree.

This is not available for Qt5 as support for it was removed:
http://trac.webkit.org/changeset/136235/trunk/Source/WebKit/qt/WidgetApi/qwebframe.h
Add option to force jpeg compression of all images as long as the jpeg compressed versions are smaller than the deflated versions (which was the pre-e5b82cd behaviour of wkhtmltopdf-qt).

Document behaviour of --image-dpi changed such that it can now be set to 0 to avoid shrinking images.