Support schema qualified stored procedures for mssql

[fdzuJ]

mssql supports execution of schema qualified stored procedures, parser panics.

use sqlparser::dialect::MsSqlDialect;
use sqlparser::parser::Parser;
 
fn main() {
    let sql = "execute some_schema.some_procedure;";
 
    let dialect = MsSqlDialect {};
 
    let ast = Parser::parse_sql(&dialect, sql).unwrap();
 
    for stmt in ast.iter() {
        println!("{}", stmt.to_string())
    }
}

ParserError("Expected end of statement, found: . at Line: 1, Column 20")