[Rpm-metadata] adding different compression types to createrepo

[Anders F Björklund]

>> Bonus points for using "import lzma" instead of "| lzma",
>> like utils.LzmaFile did*... That is, to use lzma.LZMAFile
>
> In fact, that is probably a requirement... (lzma.LZMAFile)

Fixed patch was rejected by this mailing list, but is in Unity.
It adds --lzma and --xz switches to createrepo, with pyliblzma.

Since it is using gzip by default, there should be no breakage...

Support for primary.xml.lzma and Packages.lzma is now in Smart,
along with the reading of the Mandriva media_info/info.xml.lzma.

As stable distros are still using bzip2, it'll take longer for xz.

--anders