ArrayBuffer needs regression tests

[tilmannOSG]

As discussed in #1467, we need to add a set of regression tests to have some basic test coverage of the ArrayBuffer implementation.

[tilmannOSG]

@jiangzidong Created this issue so we don't forget about the tests :)

[jiangzidong]

yes, it is a good place to ask and discuss test-related questions.

[jiangzidong]

@LaszloLango We have 2 test folders: "tests/jerry" and "tests/jjerry-test-suite". What is the difference betweem them?

[LaszloLango]

@jiangzidong, good question. :) It is quite legacy, not sure what was the intention of this. I think the jerry-test-suite was designed to use it instead of the official test262 test suite. "tests/jerry" is mostly regression tests. If we fix a bug, the related regression test must be put there. But there are some general tests too in that folder.