testsuite, objective-c++ : Add a dummy retain/release to testuite object.

testsuite, objective-c++ : Add a dummy retain/release to testuite object.

On newer systems, the throw/catch process sends retain and release
messages to thrown objects.  While these are not needed in the testsuite
cases, they cause the tests to fail because the selector is not handled.
Add dummy methods to the testsuite object.

gcc/testsuite/ChangeLog:

	* objc-obj-c++-shared/TestsuiteObject.h: Add dummy retain and
	release method declarations.
	* objc-obj-c++-shared/TestsuiteObject.m: Add dummy retain and
	release implementations.