Incorrect parameter length for char types in MicrosoftDataSqlClientDriver

[hazzik]

NHibernate.Test.Linq.FunctionTests.CharIndexFunction was failing using MicrosoftDataSqlClientDriver

=> NHibernate.Test.Linq.FunctionTests.CharIndexFunction
NHibernate: 
    select
        employee0_.FirstName as col_0_0_ 
    from
        Employees employee0_
NHibernate: 
    select
        lower(employee0_.FirstName) as col_0_0_ 
    from
        Employees employee0_ 
    where
        charindex(@p0, lower(employee0_.FirstName))-1=@p1;
    @p0 = 'a' [Type: StringFixedLength (4000:0:0)], @p1 = 0 [Type: Int32 (0:0:0)]

Note the size of @p0 parameter. Same test using Sql2008ClientDriver:

=> NHibernate.Test.Linq.FunctionTests.CharIndexFunction
NHibernate: 
    select
        employee0_.FirstName as col_0_0_ 
    from
        Employees employee0_
NHibernate: 
    select
        lower(employee0_.FirstName) as col_0_0_ 
    from
        Employees employee0_ 
    where
        charindex(@p0, lower(employee0_.FirstName))-1=@p1;
    @p0 = 'a' [Type: StringFixedLength (1:0:0)], @p1 = 0 [Type: Int32 (0:0:0)]

Closes #3280