Adminer 5.1.0

[vrana]

Version 5.1.0 includes code changes not mentioned in the release announcement because they should be invisible to users. I'll list them here:

• Test suite generated also for PDO.
• Modernized JavaScript (use let/const, use arrow functions, use for...of, removed old feature checks, use classList).
• Enabled E_NOTICE and E_STRICT error level in PHP except undefined array element.