fix the issues:
1. replace tab with space in server_bin_log.lib.php
2. move $bin_log to server_binlog.php
3. add server common function file server_common.lib.php
Merge pull request #405 from xmujay/0604_server_plugins

refactor server_plugins.php:
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Start to fix bug #3921
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Merge remote-tracking branch 'origin/QA_4_0' into QA_4_0
Merge commit 'f941036'
Fix merge conflict
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Merge remote-tracking branch 'origin/master'
bug #3921 Call to undefined function PMA_isSuperuser() if default server is not set
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Merge remote-tracking branch 'origin/QA_4_0' into QA_4_0
Fix merge conflicts
Merge commit 'c061790'
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