merge patch from Jose Paulo Moitinho de Almeida for AlternateRight/AlternateLeft transfinite options

Show label and help as tooltip; allow multi-line strings with Str[] syntax

Fopen deals with non-ASCII filename paths on Windows.

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New homology command "Betti" to compute just the Betti numbers of the given domain and relative subdomain. It is always somewhat faster than computing (co)homology basis.

- remove error in a:b:c if leads to empty list

Major work on GUI : removed much-hated "menu window" & merged onelab tree in graphic window. Gmsh now requires FLTK 1.3.

(Additional changes: fixed crash when de-minimizing opengl window on mac os ; refactored Msg::StatusBar)

To abort a script, use "Abort"

Better handling of (co)homology computation in selected dimensions only. Various cleanups and documentation of (co)homology stuff.

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