* g++.dg/lto/lto.exp: Add support for C/C++ mix language testing.

	* gcc.dg/lto/pr54625-1_0.c: Move from here...
	* g++.dg/lto/pr54625-1_0.c: ... to here.
	* gcc.dg/lto/pr54625-1_1.C: Likewise.
	* g++.dg/lto/pr54625-1_1.C: Likewise.
	* gcc.dg/lto/pr54625-2_0.c: Likewise.
	* g++.dg/lto/pr54625-2_0.c: Likewise.
	* gcc.dg/lto/pr54625-2_1.C: Likewise.
	* g++.dg/lto/pr54625-2_1.C: Likewise.

From-SVN: r203862