Write params if system is solved as REDUNDANT_OKAY.

A system solved as REDUNDANT_OKAY is still solved correctly,
even if the UI would consider this an error, in case that
g->allowRedundant==false. So there's no reason to discard this
solution; we might find it useful if a system loses a degree of
freedom while dragging, or to avoid regeneration after redundant
constraints are allowed.

This commit also reverts commit 3ff236c, as that is not necessary
anymore.

src/system.cpp

@@ -463,10 +463,8 @@ int System::Solve(Group *g, int *dof, List<hConstraint> *bad,
     if(!rankOk) {
         if(!g->allowRedundant) {
             if(andFindBad) FindWhichToRemoveToFixJacobian(g, bad);
-            return System::REDUNDANT_OKAY;
         }
-    }
-
+    } else {
         // This is not the full Jacobian, but any substitutions or single-eq
         // solves removed one equation and one unknown, therefore no effect
         // on the number of DOF.
@@ -492,7 +490,7 @@ int System::Solve(Group *g, int *dof, List<hConstraint> *bad,
                 }
             }
         }
-
+    }
     // System solved correctly, so write the new values back in to the
     // main parameter table.
     for(i = 0; i < param.n; i++) {

src/textscreens.cpp

@@ -469,7 +469,6 @@ void TextWindow::ScreenAllowRedundant(int link, uint32_t v) {
 
     Group *g = SK.GetGroup(SS.TW.shown.group);
     g->allowRedundant = true;
-    SS.MarkGroupDirty(g->h);
     SS.GenerateAll();
 
     SS.TW.shown.screen = SCREEN_GROUP_INFO;