Unused library variables causing warning messages

[rtek1000]

https://github.com/freetronics/DMD2/blob/master/DMD2_TextBox.cpp line 55:

From:
int delta = cur_y + rowHeight - height; // the amount that it's over by

To:
// int delta = cur_y + rowHeight - height; // the amount that it's over by

https://github.com/freetronics/DMD2/blob/master/DMD2_Text.cpp line 139:

From:
template <class StrType> __attribute__((always_inline)) inline unsigned int _stringWidth(DMDFrame *dmd, const uint8_t *font, StrType str)
To:
template <class StrType> __attribute__((always_inline)) inline unsigned int _stringWidth(DMDFrame *dmd, const uint8_t *, StrType str)

See discussion here:
https://forum.arduino.cc/t/how-to-resolve-this-notification-in-instantiation-of-xxxx-required-from-here