[ar] Increment line height on titles for Arabic language 

I added the line-height for all the type of title h1,h2,h3,h4,h5,h6 to fix the same font for all:

http://i.imgur.com/z70Nrv8.png
http://i.imgur.com/4sQm8M5.png
http://i.imgur.com/LPjxIAa.png