Fix PR c++/36408

gcc/cp/ChangeLog:

	PR c++/36408
	* cp-tree.h (empty_expr_stmt_p): Declare ...
	* semantics.c (empty_expr_stmt_p): ... this.
	* pt.c (tsubst_copy_and_build) <STMT_EXPR>: Use it.

gcc/testsuite/ChangeLog:
	PR c++/36408
	* g++.dg/template/stmtexpr2.C: New test.

From-SVN: r154731