Fix expect for gdb.cp/m-static.exp

Fix expect for gdb.cp/m-static.exp

The expectation in gdb.cp/m-static.exp for the ptype of
single_constructor is to get in the result of destructor with the
following prototype: ~single_constructor(int).

Yet, m-static.cc declares the destructor as ~single_constructor(). This
commit fixes the expectation.

2017-03-16  Thomas Preud'homme  <thomas.preudhomme@arm.com>

	gdb/testsuite/
	* gdb.cp/m-static.exp: Fix expectation for prototype of
	test5.single_constructor and single_constructor::single_constructor.