Rewrite "doeach" to expand to cl:loop. Now destructuring binding is possible.
Add tests of doeach.
Allow destructuring binding in a binding place of while-let. "_" will be ignored.
Allow doeach to be used with a hash-table.

Usage:
  (doeach ((key val) hash)
    (princ "${key}: ${val}\n"))
Add tests for regular expression.