Update an exception message.
Fail early.
Avoid useless \result assignements.
Declaration's iterator does not return local vars.
Add borrowing variables and \old(…) support.

A borrowing variable represents a link between two variables (kind a
redirection). It is useful to create link between pre- and post-state in
the contract, such as \old(…).
[auto] Merge from Praspel

    • #603d5d7 — Update an exception message. (Ivan Enderlin, 2013-09-16)
    • #f9ce251 — Fail early. (Ivan Enderlin, 2013-09-16)
    • #b391d74 — Avoid useless \result assignements. (Ivan Enderlin, 2013-09-16)
    • #22efd46 — Declaration's iterator does not return local vars. (Ivan Enderlin, 2013-09-16)
    • #d44a853 — Add borrowing variables and \old(…) support. (Ivan Enderlin, 2013-09-16)

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Merge remote branch 'library-praspel/master'