patch 9.0.1691: wrong viewport restored for incsearch and smoothscroll

Problem: wrong viewport restored for incsearch and smoothscroll
Solution: Save and restore skipcol as well

closes: #12713

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 00d3292..55b4632 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -122,6 +122,7 @@
 typedef struct {
     colnr_T	vs_curswant;
     colnr_T	vs_leftcol;
+    colnr_T	vs_skipcol;
     linenr_T	vs_topline;
 # ifdef FEAT_DIFF
     int		vs_topfill;
@@ -135,6 +136,7 @@
 {
     vs->vs_curswant = curwin->w_curswant;
     vs->vs_leftcol = curwin->w_leftcol;
+    vs->vs_skipcol = curwin->w_skipcol;
     vs->vs_topline = curwin->w_topline;
 # ifdef FEAT_DIFF
     vs->vs_topfill = curwin->w_topfill;
@@ -148,6 +150,7 @@
 {
     curwin->w_curswant = vs->vs_curswant;
     curwin->w_leftcol = vs->vs_leftcol;
+    curwin->w_skipcol = vs->vs_skipcol;
     curwin->w_topline = vs->vs_topline;
 # ifdef FEAT_DIFF
     curwin->w_topfill = vs->vs_topfill;