Improve regex for DB2 and AS400 URL Parser

[quaff]

1. negate char ^ should be declared only once.
2. db2 only use : as separator no ? document

@oburgosm Would you take a look at this?

[coveralls]

Pull Request Test Coverage Report for Build 320

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 50.348%

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Totals
Change from base Build 313:	0.0%
Covered Lines:	507
Relevant Lines:	1007

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💛 - Coveralls

[oburgosm]

I reviewed it and it's ok.