Of the five close reasons, exact duplicate, subjective and argumentative, and not a real question cannot apply to a category of questions. Any given question could be closed under any of those three rules, but not a whole class of questions.
Thus, two remain:
off topic
Questions on Stack Overflow are expected to generally relate to programming or software development in some way, within the scope defined in the faq.
Are Mozilla questions on topic? Yes, so long as they relate to specific code. More general software development questions, however, also have a place—on the Programmers Stack Exchange siteProgrammers Stack Exchange site. However, questions that relate to the Mozilla Foundation and not actual programming do not have a place on any current SE site.
too localized
This question would only be relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation
that is not generally applicable to the worldwide audience of the internet.
This is the tricky close reason, the one that even Meta is not totally agreed upon. That said, we are fortunate enough to have the guidance of Stack Exchange's CEO, Joel Spolsky, who recently supported striking out the part that I have just stricken out. From looking at your example questions, I don't feel they're geographically or temporally limited. As for the last category, I don't feel that they are extraordinarily narrow and if the questions are closed that way, point them to Joel's post.
Bottom line: The questions you gave as examples and similar questions seem to be acceptable on Stack Overflow. So go ahead and ask. :)