patch 9.0.0056: wrong line number reported when :cexpr fails in :def function

Problem:    Wrong line number reported when :cexpr fails in :def function.
Solution:   Set line_number before executing :cexpr. (closes #10735)
diff --git a/src/version.c b/src/version.c
index f2304f3..87a8d10 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    56,
+/**/
     55,
 /**/
     54,