fix 1348

[loxp]

Fixes #1348

Changes proposed in this pull request:

• remove set limit to null in processLimit.
• add unit test to single table select pagination, and issue sharding-jdbc单库分表查询不拆分数据表分页只能查询到第一页数据 #375 does not appear.

[coveralls]

Pull Request Test Coverage Report for Build 5706

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 7 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.4%) to 71.063%

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Files with Coverage Reduction	New Missed Lines	%
sharding-core/src/main/java/io/shardingsphere/core/parsing/antlr/extractor/statement/handler/filler/TableJoinHandlerResultFiller.java	1	40.0%
sharding-core/src/main/java/io/shardingsphere/core/parsing/antlr/extractor/statement/handler/filler/ColumnDefinitionHandlerResultFiller.java	1	96.88%
sharding-core/src/main/java/io/shardingsphere/core/parsing/antlr/extractor/statement/handler/filler/AbstractHandlerResultFiller.java	2	71.43%
sharding-core/src/main/java/io/shardingsphere/core/parsing/antlr/sql/ddl/AlterTableStatement.java	3	73.68%

Totals
Change from base Build 5701:	0.4%
Covered Lines:	8836
Relevant Lines:	12434

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💛 - Coveralls