SCCP: Fix ODR issues when compiling with LTO [PR 113054}

The problem here is that in C++ structs and classes have a
linkage too so the type vertex is not considered local to
the TU but will conflict with the globally defined one
in graphds.h.  The simple way to fix this is to wrap the ones
defined locally in gimple-ssa-sccopy.cc inside an anonymous namespace
and they are now considered locally to that TU.

Committed as obvious after a bootstrap/test on x86_64.

gcc/ChangeLog:

	PR tree-optimization/113054
	* gimple-ssa-sccopy.cc: Wrap the local types
	with an anonymous namespace.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>