Allow builder to work simply on multiple vnum at once.
Tested through Valgrind without problems, but not caring about ridiculously large selections, so code is not totally 'safe'.

use case:
selection show: obvious
selection clear:obvious
selection 1 10 (creates a 1 2 3 4 5 6 7 8 9 10 array)
selection 2 array become 1 3 4 5 6 7 8 9 10
selection 2 array become 1 2 3 4 5 6 7 8 9 10

selection titi
selection toto
selection tata
-> tata titi toto (it is ordered)

loop 10 say hello will make you say hello 10 times
loop seletion say <xxx> will make you say tata say titi say toto (basically what was in your selection replaces the <xxx>