CLEANUP: Use ist2(const void*, size_t) whenever possible

Refactoring performed with the following Coccinelle patch:

    @@
    struct ist i;
    expression p, l;
    @@

    - i.ptr = p;
    - i.len = l;
    + i = ist2(p, l);
diff --git a/src/wurfl.c b/src/wurfl.c
index 02e1dd4..6030c4c 100644
--- a/src/wurfl.c
+++ b/src/wurfl.c
@@ -742,8 +742,7 @@
 		return NULL;
 	}
 
-	name.ptr = (char *)header_name;
-	name.len = strlen(header_name);
+	name = ist2((char *)header_name, strlen(header_name));
 
 	// If 4th param is set, it works on full-line headers in whose comma is not a delimiter but is
 	// part of the syntax