If you do use core.js for JText::script always, then I would suggest make there nicer: html/renderer/head.php#L220-L234

I have just changed as you have proposed. That is better solution.

you understood me wrong
JHtml::_('script', 'system/core.js', false, true); can be where you did it first,
It will not work as you did now, because all scripts already rendered.

I mean other,
I mean that part of the code that on html/renderer/head.php#L220-L234 is unneeded after applying this pull request. So would be good clean up there
This code is allow Joomla.JText works when core.js not loaded, but it have no sense if core.js will be available

Currently, core.js has a dependancy on mootools. So you should never load core.js without mootools. Thus currently the way to load it is JHtml::_('behavior.framework');.
We will need a new way to load core.js as soon as it's rewritten for jQuery (or to use no dependancy at all). My suggestion would be to use a new function JHtml::_('behavior.core') by then. I made a PR a while ago to prepare for that: #3047.
I'm not a huge fan of loading it with JHtml::_('script', 'system/core.js', false, true); as this would still load mootools after it is converted to jQuery with #2687

Now I have made it incorrect. I am loading core.js to late. We can remove this part of code
https://github.com/joomla/joomla-cms/blob/staging/libraries/joomla/document/html/renderer/head.php#L225-L229 and L231. Rest has to stay to load language strings.
I will have a look at core.js and maybe I will rewrite it to jQuery if there isn't already some PR

I have just updated with all yours suggestions.

Merged to 3.3-dev

@wilsonge mentions this is not present in staging or 3.4-dev. Re-opening to ensure it's merged.

@piotrmocko Can you update the PR to use the new JHtml::_('behavior.core'); since it's available and rewritten to use jQuery since Joomla 3.3.

I have just updated code to use new core dependence

Merged this into staging again :) Thanks again!