Automatically dedent right paren/right bracket

[vosen]

We now have a simple smart indent implementation in VisualSRustSmartIndent.cs.
This is good, but slightly annoying when it comes to right paren/right bracket insertions
For example, without auto dedention:

fn foo() {
····bar();
····baz();

now inserting } at the end of the file leads to

fn foo() {
····bar();
····baz();
····}

Auto dedention should correct it to

fn foo() {
····bar();
····baz();
}

Note, that autodedention should know know the difference between } and ) and auto-dedent to the "level" of the right token.