Fix esx* package names to exs*

* esx64, esxplus, esx1024 -> exs64, exsplus, exs1024

* See https://github.com/ninenines/erlang.mk/pull/129#issuecomment-56919453
  Thx @ddosia
Merge branch 'jj1bdx-prngs-fix' of git://github.com/jj1bdx/erlang.mk