Fix two buglets in cp_print_value_fields patch

Fix two buglets in cp_print_value_fields patch

Pedro and Tom both pointed out issues in the cp_print_value_fields
patch, aka the fix for PR c++/20020.

This patch addresses both issues.  Tested on x86-64 Fedora 29.

gdb/ChangeLog
2019-06-27  Tom Tromey  <tromey@adacore.com>

	* cp-valprint.c (cp_print_value_fields): Pass opts, not options,
	to cp_print_static_field.

gdb/testsuite/ChangeLog
2019-06-27  Tom Tromey  <tromey@adacore.com>

	* gdb.cp/constexpr-field.exp: Use setup_xfail.