Build fixes and --wxidir

Your github repo is not up-to-date so this has some extra commits.  The interesting ones are

    608cc1e (build: lower gio and libxml2 requirements for wixl, 2013-01-16)
    acd4dde (wixl: do not use g_hash_table_add, 2013-01-17)
    d32e547 (build: libuuid dependency is now mandatory, 2013-01-17)
    0bfeae9 (build: add dist-xz, 2013-01-17)
    66b6c00 (msibuild: add missing include file, 2013-01-17)
    c86ecd2 (wixl: add --wxidir option, 2013-01-17)

The last is inspired by `aclocal --acdir`, and lets the testsuite use the .wxi files you built.