Use system implementation of 'array' if present.  Deprecate constructor array(const T& t) because the libstd++ implementation doesn't have it

[[Imported from SVN: r4933]]

Added a class 'array' which provides the same functionality as FixedArray, but conforms to the naming
of the tr1 array class.  I would have liked to put this into a separate header, but unfortunately,
array.hh exists already.  In a future step, the stl implementation of 'array' will be used when
available.

[[Imported from SVN: r4895]]

[[Imported from SVN: r3086]]

File, ebenso Vec, daß sich in fixedvector.hh befindet.
Außerdem erbt Vec jetzt von FixedArray.  Leider sind
einige Änderungen nicht rückwärtskompatibel.  Insbesondere
fehlen Vec::print (man nehme stattdessen operator<<)
und Vec::read (man nehme const T& operator[])
Entschuldigt die Unannehmlichkeiten.

[[Imported from SVN: r503]]