Enable math functions about direct-sqlite

[jchia]

I've added a flag to enable built-in math functions.

[johannesgerer]

Great, thank you. After looking into it a bit more, I found that the 'default' Sqlite binary for windows and in most Linux distributions has many flags enabled by default.

The way they become activated (I guess) is because the sqlite make files are used which enable them.
For example for windows or linux

Not sure whether this library should try to use them as a default, just wanted to mention this for future reference.

[jchia]

Which Linux distros has enabled the built-in math functions for their packaged sqlite? Ubuntu 20.04 is not one of them.