allow firebird.log location to be set from config or environment variable

[hmoffatt]

It would be helpful to be able to configure the location of firebird.log from an environment variable, or from the config file, or both. Currently it can only be configured at compile time.

My use case: we ship Firebird as the embedded database in our application. The files are installed in \Program Files which is not writable by the users running the application, so no logging is possible. We'd like to set it via environment variable to a path in the user's profile which will be writable.

[TommiPrami]

This would be nice, never thought about it in our embedded installations.

Some "macros" would be cool, that could have sonething like this (on windows, linux something different)

LogLocation=%AppData%\MyApp\Logs\Firebird

Or something like that...