EAPI 3_pre2 with support for installation prefix and xz unpack

In portage-2.1.7.14 and 2.2_rc59 there is support for EAPI 3_pre2, which adds support for installation prefix variables (ED, EPREFIX, and EROOT) and support for unpack of *.xz compressed files. Bug 296700 tracks EAPI 3 support in portage, and bug 273620 is for the EAPI 4 stuff that used to be in EAPI 3 but got delayed.