Merge xbps-src code to make it usable in a standalone mode.

The new xbps-src configuration file is `etc/conf` where you can
add your local overrides from defaults set via `etc/defaults.conf`.

To use this xbps-src, run these steps:

	$ make
	$ sudo make setup (to make chroot helper setgid)
	$ ./xbps-src ...

common/xbps-src/libexec/xbps-src-genpkg.sh

@@ -0,0 +1,52 @@
+#!/bin/bash
+#
+# Passed arguments:
+# 	$1 - pkgname [REQUIRED]
+#	$2 - path to local repository [REQUIRED]
+# 	$3 - cross-target [OPTIONAL]
+
+if [ $# -lt 2 -o $# -gt 3 ]; then
+	echo "$(basename $0): invalid number of arguments: pkgname repository [cross-target]"
+	exit 1
+fi
+
+PKGNAME="$1"
+XBPS_REPOSITORY="$2"
+XBPS_CROSS_BUILD="$3"
+
+. $XBPS_SHUTILSDIR/common.sh
+
+for f in $XBPS_COMMONDIR/helpers/*.sh; do
+	source_file "$f"
+done
+
+setup_pkg "$PKGNAME" $XBPS_CROSS_BUILD
+
+for f in $XBPS_COMMONDIR/environment/pkg/*.sh; do
+	source_file "$f"
+done
+
+if [ "$sourcepkg" != "$PKGNAME" ]; then
+	# Source all subpkg environment setup snippets.
+	for f in ${XBPS_COMMONDIR}/environment/setup-subpkg/*.sh; do
+		source_file "$f"
+	done
+
+	${PKGNAME}_package
+	pkgname=$PKGNAME
+fi
+
+if [ -s $XBPS_MASTERDIR/.xbps_chroot_init ]; then
+	export XBPS_ARCH=$(cat $XBPS_MASTERDIR/.xbps_chroot_init)
+fi
+
+# Run pre-pkg hooks.
+run_pkg_hooks pre-pkg
+
+# Run do-pkg hooks.
+run_pkg_hooks "do-pkg"
+
+# Run post-pkg hooks.
+run_pkg_hooks post-pkg
+
+exit 0