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 ...
.gitignore: update.