Change the interfaces for backend methods that create statements to
    always pass in the enclosing Bfunction for the statement.  Having the
    function available simplifies things if a temporary variable has to be
    created during the construction of a statement.
    
    This also includes a change to the Mark_lvalue_varexprs helper
    class to handle indirections on the left hand side of assignments
    (e.g. "*x.y = ...").
    
    Reviewed-on: https://go-review.googlesource.com/34471

	* go-gcc.cc (Gcc_backend::expression_statement): Add Bfunction*
	parameter.
	(Gcc_backend::init_statement): Likewise.
	(Gcc_backend::assignment_statement): Likewise.
	(Gcc_backend::if_statement): Likewise.

From-SVN: r243766