Added "libuv" to "gentoo".
Updated "dwm" configuration in "gentoo".
Minor formatting fix in "gentoo/package.mask".
Added "$METRO_LDFLAGS" variable to "gentoo/make.conf".
Gave "@metro" a GUI in "gentoo".
Updated "$METRO_USE" variable in "gentoo/make.conf".
Tuned "$METRO_USE" variable in "gentoo/make.conf".
Updated header levels in "README".
Updated "Structure" under "Details" in "README".
Documented inclusion of "X.Org GUI" in "README".