Remove PackagesOnHold from xbps.conf; use xbps-pkgdb -m hold|unhold instead.

To put a package on hold mode:
	$ xbps-pkgdb -m hold foo

To unhold the package:
	$ xbps-pkgdb -m unhold foo

To list packages on hold mode:
	$ xbps-query -H

This also close #12 from github.

etc/xbps.conf

@@ -41,15 +41,6 @@ repositories = {
 	#http://xbps.nopcode.org/repos/current/nonfree
 }
 
-# Packages on hold.
-#
-# Packages that are put on hold won't be updated when running a full
-# system upgrade, these packages must be updated manually.
-#
-# Package names and shell wildcards can be specified.
-#
-#PackagesOnHold = { "glibc-*" }
-
 # Virtual packages.
 #
 # The following syntax is used: