Add buffer object versions of several functions

Some of these are new ES3 functions, some are existing ES2 functions
that can now use the new pixel pack/unpack buffer bindings.

glDrawElementsInstanced needs a special case since the pointer/offset
arg isn't the last one like the generator assumes.

Bug: 8566953
Change-Id: I638a36b0a31aefcb5bfee6f4d049348223045103