Application does not build anymore

[BatchDrake]

Hi,

Pulling from master, the application does not build anymore. The problem is that out_mysql.h defines a variable named my, which gets included in many places and thus defined everywhere. This makes the same global symbol to be defined in different files, resulting in linker errors.

The workaround is to remove that deifnition from out_mysql.h and turn it into an extern variable instead.