Android Browser 4.4 calc() support

Android Browser 4.4 lacks the ability to multiply and divide values.
This means `calc(100vw - 20px)` will work but `calc(100vw / 2)` or `calc((100vw - 30px) * 250 / 715)` (actually used in my fluid layouts!) will not work.
Chnaged "p" to "a" in compatibility list
Merge pull request #781 from alexander255/patch-1

Android Browser 4.4 calc() support