Massive changes to allow installing pkgs in a chroot.

Some changes include:
 - Xstow is not used anymore, files are copied into masterdir.
 - a new target install-chroot has been created.
 - a new meta-template xbps-base-chroot has been created required for
   the install-chroot target.
 - Removed XBPS_SYSCONFDIR, /etc is used by default.
Other changes that I cannot remember right now...

--HG--
extra : convert_revision : fb57d9dafb56aeb03cc935580172e075ce584fd5

templates/sed.tmpl

@@ -3,6 +3,7 @@ pkgname=sed
 version=4.1.5
 distfiles="http://ftp.gnu.org/gnu/$pkgname/$pkgname-$version@.tar.gz"
 build_style=gnu_configure
+configure_args="--bindir=$XBPS_DESTDIR/$pkgname-$version/bin"
 short_desc="The GNU stream editor"
 maintainer="Juan RP <xtraeme@gmail.com>"
 checksum=be955bef7a81d69222e929689e0de0ecf64c13dc5b15b2ee5696d5ef66fdeec0