patch 8.0.0575: using freed memory when resetting 'indentexpr'

Problem:    Using freed memory when resetting 'indentexpr' while evaluating
            it. (Dominique Pelle)
Solution:   Make a copy of 'indentexpr'.
diff --git a/src/version.c b/src/version.c
index 28fe0b7..60dbdf4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    575,
+/**/
     574,
 /**/
     573,