Error checking for SOLVE procedure.

[1uc]

When doing

SOLVE proc

where proc is a PROCEDURE, the behaviour in NOCMODL is to check the return code of proc if it indicates failure, the failure is propagated. In the current implementation of NMODL, the return code is ignored and the failure is treated as success. This choice was made purely to be able to progress on other topics.

The task of this issue is to review the behaviour, and then likely make it consistent with NOCMODL.