postgresql writer bug

在PostgreSQLwriter中，如果表的数据类型是char(2),那么在导数据的时候，会将数据强制转成char，而不带长度的char默认长度为1，导致数据被截断丢失。

举例：
INSERT INTO t_table (col) values('01':char);

在数据库查询时发现该表字段对应的列数据为'0 '，而不是'01'，正确做法是需要将'01'转成varchar或者char(2)；
如：
INSERT INTO t_table (col) values('01':char(2));
INSERT INTO t_table (col) values('01':varchar);

见代码：postgresqlwriter/src/main/java/com/alibaba/datax/plugin/writer/postgresqlwriter/PostgresqlWriter.java 75行

Start at postgresqlwriter/src/main/java/com/alibaba/datax/plugin/writer/postgresqlwriter/PostgresqlWriter.java around line 75 and inspect how values are cast for PostgreSQL inserts. Reproduce the case with a char(2) column and the value '01'; done means the stored value remains '01' instead of being truncated, using the appropriate cast described in the issue.

Written by the indexing model from the issue text.