Rework perfect foresight handling of initial and terminal values
- Disentangle the purpose of various blocks (see https://archives.dynare.org/DynareWiki/DeterministicSimulationBlocks)
- Eliminate reuse of
oo_.steady_state
for different purposes. - Phase out the global variables
ex0_
andys0_
used inmake_ex_
andmake_y_
Related to preprocessor#104 (closed) and #1866 (closed)