problems with character encodings
Why3 IDE can display source files even if then contain UTF8 characters.
However, the message window is not robust against those characters, e.g. the file
predicate in_range (x : int) = -128 ≤ x ≤ 127
generates a syntax error that is NOT displayed in the message window (stderr contains 'Gtk-CRITICAL **: gtk_text_buffer_emit_insert: assertion 'g_utf8_validate (text, len, NULL)' failed ')