Multiple improvements for XBPS_PREFER_BINPKG_DEPS.

- Added a new var XBPS_REPO_LIST for the conf file, to specify
  a list of remote repositories to be used in a masterdir.
- Install all required binpkgs in one pass, if that fails install
  one of them at every pass.
- Fixed xbps-src-chroot-helper to properly catch SIG{INT,QUIT}
  when -m is specified.
- Misc cosmetics improvements.

--HG--
extra : convert_revision : 0ad7d559477ccc1fc04ab09deb791343ee453de6

xbps-src/libexec/xbps-src-chroot-helper.sh.in

@@ -24,9 +24,6 @@
 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #-
 
-# Umount stuff if SIGINT or SIGQUIT was caught
-trap umount_chroot_fs INT QUIT
-
 HANDLER="$1"
 
 . @@XBPS_INSTALL_ETCDIR@@/xbps-src.conf
@@ -35,6 +32,9 @@ if [ -n "${MASTERDIR}" ]; then
 	export XBPS_MASTERDIR="${MASTERDIR}"
 fi
 
+# Umount stuff if SIGINT or SIGQUIT was caught
+trap umount_chroot_fs INT QUIT
+
 REQFS="sys proc dev xbps"
 
 mount_chroot_fs()