assign external ring elements to external variables in CommonHomalgTableForMapleHomalgTools

by suppressing "need_output" in
. Minus
. DivideByUnit
. Gcd
. CancelGcd
increased version number
Added CommonHomalgTableForSingularTools entry Evaluate

depends on HomalgToCAS v2013.06.01
HomalgRingOfIntegersInSingular cannot pass rational parameters!
Zero, One, and MinusOne now have true pointers
an enter
sorted entries in CommonHomalgTableForSageTools
Updated parameter list of Evaluate
added Vinay as author
Perform( var, ... SetName ) -> Perform( var, Name )
removed Error messsage if indeterminate does not yet have Name set

Error( "the indeterminates of the base ring must all have a name (use SetName)\n" );
make _MAGMA_SetRing more robust

it now passes the names of the indeterminates rather than their pointers
(this is necessary in future when we completely abondon strings as pointers)
make RP!.SetInvolution for Singular more robust

it now passes the names of the indeterminates rather than their pointers
(this is necessary in future when we completely abondon strings as pointers)