DEV: coccinelle: Add a new pattern to ist.cocci

This was previously ignored in "DEV: coccinelle: Fix incorrect replacement in ist.cocci",
but is now properly replaced by a simple `ist()` call.
diff --git a/dev/coccinelle/ist.cocci b/dev/coccinelle/ist.cocci
index ea13d39..acde626 100644
--- a/dev/coccinelle/ist.cocci
+++ b/dev/coccinelle/ist.cocci
@@ -4,8 +4,9 @@
 @@
 
 (
- i.ptr = p;
- i.len = strlen(i.ptr);
+- i.ptr = p;
+- i.len = strlen(i.ptr);
++ i = ist(p);
 |
 - i.ptr = p;
 - i.len = l;