See Revert "zope patches: display OFSFile content using full available height in zmi".

This fixes testBigFile failures because of `size` not being set to 0 when `data`
is set to None.

Modify DTML templates likewise Zope4 removal commit:
  commit 1df76c1ea8911d7d9249eb6beab1fafd4ed5803c
  Author: Hanno Schlichting <hanno@hannosch.eu>
  Date:   Sun Jul 3 14:19:26 2011 +0000
      Removed `bobobase_modification_time` from `Persistence.Persistent`, you can use `DateTime(object._p_mtime)` instead.

This fixes failure on test_PROPFIND_on_document (testWebDavSupport).

also use the same pattern of clickAndWait and assertElementPresent
in all places, sometimes we used click and waitForElementPresent,
which should be equivalent because we click on a top level navigation
link

This reverts commit 8f5497d4.

This is not longer needed - with Zope 4 the ZMI is better and we now
have possibility to edit most of these through ERP5 user interface.
The main motivation is that these kind of patches are really hard to
keep up to date.

This reverts commit 88786a70.

This is not longer needed - with Zope 4 the ZMI is better and we now
have possibility to edit most of these through ERP5 user interface.
The main motivation is that these kind of patches are really hard to
keep up to date.

This reverts commit c89e308f.

This is not longer needed - with Zope 4 the ZMI is better and we now
have possibility to edit most of these through ERP5 user interface.
The main motivation is that these kind of patches are really hard to
keep up to date.

In the changes from ExternalMethod 2.13.1 -> 4.5, now ExternalMethod
define __code__ (and __defaults__) to a computed attribute calling
getFunction, but getFunction is different in our patched class, so
when unwrapMethod tries to get __code__, it will raise and mapply
will not consider the external method as being callable, so a simple
__repr__ of the ExternalMethod will be used as response body when
published.

By defining __code__ to something using our patched logic, this
problem does not happen.

Utility function taking care of the internal changes between RestrictedPython v3
and v5, keeping support for both (instead of having multiple if statements).

* Emtpy parameter.
* No argument.