C++17 u8 character literals testcase

Issue #1450

Examples/test-suite/cpp17_u8_char_literals.i

@@ -0,0 +1,8 @@
+%module cpp17_u8_char_literals
+
+%inline %{
+// UTF-8 character literals will (apparently) have type char8_t in C++20.
+char a = u8'a';
+char u = u8'u';
+char u8 = u8'8';
+%}

Examples/test-suite/python/cpp17_u8_char_literals_runme.py

@@ -0,0 +1,10 @@
+from cpp17_u8_char_literals import *
+
+if cvar.a != 'a':
+    raise RuntimeError
+
+if cvar.u != 'u':
+    raise RuntimeError
+
+if cvar.u8 != '8':
+    raise RuntimeError