Add bufferSubData and clearBuffer[fiuv] to immutable slice whitelist

[RSSchermer]

Adds bufferSubData and clearBuffer[fiuv] to immutable slice whitelist.

Edit: bufferData -> bufferSubData (typo)

[alexcrichton]

Thanks for the PR! I'm personally pretty unfamiliar with WebGL, but @chinedufn perhaps you'd be willing to take a look to verify this is a correct transformation to apply?

[RSSchermer]

Here are some links the the relevant MDN documentation to perhaps help verify that these function indeed don't require and exclusive reference:

• bufferSubData
• clearBuffer

[alexcrichton]

Ok yeah sounds like @chinedufn is busy right now so looks good to me!