Minor enhancements + Bug

Generalized get...() formulas
Moved the calling of vanity gen to its own function

Program takes 3 strings from user, picks one randomly, encrypts it with
xor char by char, saves it to the file "seed," then vanitygen uses it as
the seed for generating an address. Rinse and repeat

Bug: Vanitygen seems to randomly crash and "stop working." Unknown as to
why. Doesn't seem to be related to a certain malicious byte being in
seed file. Might be because it is being called multiple times per
second.