Add testcase for nested inner class deriving from a templated base class and defined outside of the outer class.

For languages that don't support nested class support, use flatnested.
See issue #270

Examples/test-suite/common.mk

@@ -299,6 +299,7 @@ CPP_TEST_CASES += \
 	nested_directors \
 	nested_comment \
 	nested_scope \
+	nested_template_base \
 	nested_workaround \
 	newobject1 \
 	null_pointer \