Copy over fix for fetching dynamic type of a reference from python side.

	* guile/scm-value.c (gdbscm_value_dynamic_type): Use coerce_ref to
	dereference TYPE_CODE_REF values.

	testsuite/
	* gdb.guile/scm-value.c: Improve test case.
	* gdb.guile/scm-value.exp: Add new test.