gdb/testsuite/gdb.cp: Fix tests for ARM C++ ABI.

gdb/testsuite/gdb.cp: Fix tests for ARM C++ ABI.

The ARM C++ ABI defines constructors and destructors to return
pointers to this. The C++ tests that check the types of constructors
and destructors expect a return type of void. Conditionalize these
tests so they pass on ARM.

gdb/testsuite/ChangeLog:

2013-06-07  Will Newton  <will.newton@linaro.org>

	* gdb.cp/anon-struct.exp: Conditionalize constructor and
	destructor prototypes for ARM ABI.
	* gdb.cp/m-static.exp: Likewise.