[ODBC] char/SQLCHAR casting needed

[blumf]

Throughout the ls_odbc.c code there is mixing of char and SQLCHAR types. Not a real problem but will need casting to avoid compile warnings.

[vespadj]

About this, I connect to sql server, the data type is "nvarchar" , lua says "Assertion failed", so for each field I need to use CAST(fieldname AS text).
Please consider to insert these common datatypes in ls_odbc.c (lines 160)

http://msdn.microsoft.com/en-en/library/ms187752.aspx

[blumf]

I'm pointing this to #36