we now introduce explicit copy functions whenever type_constraint is applied to convert between scalar/non-scalar representations

uses static inlined C functions to perform the nodetype
checks for each assignment and gives and error messages
and segfaults whenever a mismatch is detected.

and their corresponding return type does not match. This is done to
ensure that the backend emits corresponding representation adjustments.

implemented a facility which sets the correct linksigns for the SPMD-functions.

However, when compiling classes/random/Rand.sac, a global object appears in an afterguard. This then kills MMV. Since I have no idea how global objects should be handled wrt constraint checks, I would like someone else to have a look at it.

Fixed some problems with void functions in SOSSK and problems with [0,...] shaped indexvectors in Oversel.

whether it beeing a ret or an arg. This shall be ignored.

and moved it accordingly.

Fixed two errors, one which occures if a variable is not used on RHS below LHS occurences and one belonging to extern functions.