Column count stays from previous query for queries not returning resultset

If after SELECT(or catalog function, or SQLGetTypeInfo), application runs smth like UPSERT, and then examines SQLNumResultCols, it will return number of columns in previous resultset. This is what issue#4 from github boils down to.

The testcase:

ODBC_TEST(t_odbc41)

{ SQLSMALLINT cols_count; OK_SIMPLE_STMT(Stmt, "drop table if exists t_odbc41"); OK_SIMPLE_STMT(Stmt, "SELECT 1, 2, 3, 4"); CHECK_STMT_RC(Stmt, SQLFetch(Stmt)); CHECK_STMT_RC(Stmt, SQLNumResultCols(Stmt, &cols_count)); is_num(cols_count, 4); CHECK_STMT_RC(Stmt, SQLFreeStmt(Stmt, SQL_CLOSE)); OK_SIMPLE_STMT(Stmt, "CREATE TABLE t_odbc41 (id INT PRIMARY KEY auto_increment)"); CHECK_STMT_RC(Stmt, SQLNumResultCols(Stmt, &cols_count)); is_num(cols_count, 0); OK_SIMPLE_STMT(Stmt, "drop table if exists t_odbc41"); return OK; }