Added DC-9, MD-90, & B727 to use correct tail mounted engines icon

[rparenton]

No description provided.

[wiedehopf]

They should have already had that icon due to their wake turbulence class and stuff.
Explicit doesn't hurt though and scaling for 727 is good.

thank you.

[rparenton]

Thanks for merging this. FWIW, I've seen at least two DL MD-90s in the past day or so that were using the standard 'airliner' icon. That's what prompted me to look closer.