[vala/staging] Sync NEWS from 0.54

[Rico Tzschichholz <ricotz src gnome org>]

commit e73a038895c2f79555bae2bf5a4c25bd345a823f
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Sat Jan 8 21:49:40 2022 +0100

    Sync NEWS from 0.54

 NEWS | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
---
diff --git a/NEWS b/NEWS
index 3a6c1ffcd..6aff076bf 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,18 @@
+Vala 0.54.6
+===========
+ * Various improvements and bug fixes:
+  - codegen:
+    + Allow boxing of non-external SimpleType structs [#1273]
+    + Cast given default-value of struct with possible member initializer [#1272]
+    + Clear existing length values when revisiting a slice expression [#1274]
+  - vala:
+    + Allow unsafe assignment of integer to enum while reporting a notice
+    + Non nullable enum types are simple types [#1268]
+    + Correctly replace "in" expression in pre-/postconditions of method [#1269]
+
+ * Bindings:
+  - gio-2.0: Add custom MemoryOutputStream.with_*data() wrappers [#1271]
+
 Vala 0.54.5
 ===========
  * Various improvements and bug fixes: