Description of problem:
implement IFERROR() function in spreadsheet formulae as defined in:
http://tools.oasis-open.org/issues/browse/OFFICE-3468

there is threefold motivation for it:
  * it's defined in ODF
  * it's much more convenient and error-resistant to write IFERROR(expr;value)
    instead of IF(ISERROR(expr);value;expr)
  * it's extensively uses in documents created in other spreadsheets (Gnumeric,
    MS Excel) and it is a compatibility issue when interoperating with users
    of said programs

Version-Release number of selected component (if applicable):
libreoffice-calc-3.4.5.2-9.el6.x86_64

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