Add palemoon-9999 for building from Git

[ghost]

It would be really appreciated if you made a way to build Palemoon directly from Git as there are bugfixes that haven't been released yet.

[Bfgeshka]

@mattatobin how's so?

[deu]

Well, there are also a couple of other little changes that are going to be needed (just ebuild-related stuff, nothing that would change things on Pale Moon's side). I've been hesitant about adding this because I won't be using it and I wouldn't be able to test the ebuild other than cursorily when changes are made. Maybe I'll add a big yellow warning making clear that no support will be given if people still want to use it.

[nado]

Are there even some people compiling a live git project thinking about asking support instead of filing a bug report? Unless it is the random testers you don't want I don't see what changes from other -9999 ebuilds.

And isn't the branding issue the same for every version ? Since it is the end user who compiles PM, it is they who should be advised not to redistribute the compiled version with branding enabled. Or did I get something wrong?