[tuples] fix libjava PR6729

It turns out the assertion was a bit too strict, as
declare_return_variable() which was used in computing STMT, was
sometimes adding a NOP/CONVERT_EXPR.

Committing to branch.

    * tree-inline.c (expand_call_inline): Allow casts in assert.

Index: tree-inline.c
===================================================================
--- tree-inline.c    (revision 138092)
+++ tree-inline.c    (working copy)
@@ -3347,7 +3347,9 @@ expand_call_inline (basic_block bb, gimp
the equivalent inlined version either. */
if (is_gimple_assign (stmt))
{
- gcc_assert (gimple_assign_single_p (stmt));
+ gcc_assert (gimple_assign_single_p (stmt)
+         || gimple_assign_rhs_code (stmt) == NOP_EXPR
+         || gimple_assign_rhs_code (stmt) == CONVERT_EXPR);
TREE_USED (gimple_assign_rhs1 (stmt)) = 1;
}