Preprocessor update

– Add two missing checks for file opening failures
– Run detrending engine if trend variables are present, even if unused in a
  var(deflator=…) statement
– Remove some incorrect normalization rules for the case mfs=3
  As a consequence, increase the tolerance for a test with mfs=3 (it now uses
  the same tolerance as the corresponding test for mfs=2).

preprocessor @ 3699a2de

-Subproject commit 0301595516cf9be594123c8f15e89a9a2363174d
+Subproject commit 3699a2defdb31cc8dfa45ff7a447a4ab29a7f31e

tests/block_bytecode/lola_solve_one_boundary_mfs3.mod

@@ -7,6 +7,6 @@
 
 mfs0=load(['lola_solve_one_boundary' filesep 'Output' filesep 'lola_solve_one_boundary_results']);
 
-if max(max(oo_.endo_simul-mfs0.oo_.endo_simul)) > options_.dynatol.x
+if max(max(oo_.endo_simul-mfs0.oo_.endo_simul)) > 20*options_.dynatol.x
    error('Inconsistency with mfs=0')
 end