Issue #2156 : speed up JarAnalyzer

[idodeclare]

Hello,

Please consider for integration this patch to speed up JarAnalyzer by reusing the same string builders for an entire jar.

Thank you.

[coveralls]

Pull Request Test Coverage Report for Build 2562

• 39 of 39 (100.0%) changed or added relevant lines in 3 files are covered.
• 13 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.004%) to 72.831%

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Files with Coverage Reduction	New Missed Lines	%
src/org/opensolaris/opengrok/history/SCCSRepository.java	1	79.27%
src/org/opensolaris/opengrok/configuration/IndexTimestamp.java	2	52.38%
src/org/opensolaris/opengrok/history/HistoryGuru.java	2	75.4%
src/org/opensolaris/opengrok/configuration/RuntimeEnvironment.java	2	71.43%
src/org/opensolaris/opengrok/history/RepositoryFactory.java	3	86.27%
src/org/opensolaris/opengrok/history/BitKeeperRepository.java	3	79.72%

Totals
Change from base Build 2561:	-0.004%
Covered Lines:	31182
Relevant Lines:	42814

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💛 - Coveralls

[tarzanek]

it looks ok, merging, thank you