g++.exp (g++_init): Use istarget.

g++.exp (g++_init): Use istarget.

	* lib/g++.exp (g++_init):  Use istarget.  Remove target_triplet global.
	* lib/obj-c++.exp (obj-c++_init): Ditto.
	* lib/file-format.exp (gcc_target_object_format): Ditto.
	* lib/target-supports-dg.exp (dg-require-dll): Ditto.
	* lib/target-supports-dg-exp (check_weak_available): Ditto.
	(check_visibility_available): Ditto.
	(check_effective_target_tls_native): Ditto.
	(check_effective_target_tls_emulated): Ditto.
	(check_effective_target_function_sections): Ditto.

From-SVN: r176240