Adjusted pattern for matching media links to properly handle a single '}' in the link text. Fixes #1587.

This fixes a problem with those tests in the most recent version of
phpunit. I thought it was caused by the use of the deprecated var
keyword, but some other weirdness was going on. This way it's more
proper anyway.

This should fix some tests on PHP 7.1. The work is far from done, we
still have a lot of variables without proper accessibility defined.

Those tests either just check that an exception is NOT thrown or are
there to check dependencies for other tests. Newer phpunits mark all
tests as risky that have no assertion.

actually we could right now. but I don't like to introduce that change in
a feature branch.

We still need 5 to test on old php versions, but travis uses 6 for newer
PHP versions (and 5 may break on those).

Luckily both versions aren't that far apart, yet. This adds a thin
adapter class when running on 6.

See for reference #1837 and sebastianbergmann/phpunit#2503

However those classes are already supported in PHP 5.7 so we can switch
to them without breaking backward-compatibility.

This makes it more flexible to use on the expense of needing one echo
more.

now comments and line breaks between tags are removed

Without the change in issue #1801, or commit
1b26d16d respectively, this adjusted
test would throw an error since it would attempt to use another array as
an array-key.

The fact that the test passes without error means that the bug is fixed.

What happened was that in the place of the new `waitForTick`-call an
actual delay happened and therefore the file modification time and the
deletion entry were two different points in time, resulting in random
test failures. The test enforces this now, the condition to test has
been adjusted.

Multiple selected option would not be valid HTML.

Now each command is checked within it's own test on a completely clean
install. Hopefuly this also takes care of the flaky test behavior seen
at Travis occasionally.

Some of our tests require that at least one second has passed before
they can continue because our revisions depend on the Unix Timestamp.

Currently we use a sleep(1) for this. However this always waits a whole
second, even if the next second is already much closer or maybe already
here - especially when some processing has been done since the last
operation.

This new method waits for the next second by checking the time every
10th of a second. This might speed up some of our tests a bit.

This took me way to long to figure out. The useheading setting was
cached in a static variable which is fine usually as it doesn't change
during a single request. But in testing we want to change it often.

getMock is deprecated in new PHPUnit versions and createMock is the
recommended replacement. However that one is not available in older
PHPUnit releases. Since we still support older PHP releases we have to
support older PHPUnit releases as well.

This add some compatibility functions to our TestCase class and replaces
all calls to getMock. Tested with PHPUnit 4.6.6 and 5.5.0.

Using an HTML entitiy might be problematic in non HTML renderers or when
the output is escaped again.

this hopefully helps with recent problems of spradically failing tests.