added Texas Instruments S-PWSON-N8, with&without thermal vias

Created by: jkriege2

• datasheet: http://www.ti.com/lit/ds/symlink/lp2951.pdf
• used for LP2951: https://github.com/KiCad/kicad-symbols/pull/564
• remaining Travis errors are due to the thermal vias ... hope I got them right!

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