Limit number of stored errors to 20
Limit number of stored errors to 20

Anyway the first error is usually the most interesting one.

Fixes #138

Signed-off-by: Michal Čihař <a2df1e659c9fd2578de0a26565357cb273292eeb@cihar.com>

phpmyadmin/error-reporting-server,phpmyadmin/error-reporting-server,phpmyadmin/error-reporting-server