ES 3.0 strong enums for DrawArrays*() and Draw*Elements*()

The strongly-typed enums include core and extension varieties.
ES 3.0 strong enums for DrawBuffersEXT and NV

Relax the extension constraint in DrawBuffers, in order to add strong
enums to the extension varieties of this function.
ES 3.0 fixed enums for GetInteger64*

GetInteger64v should accept GetPName, while GetInteger64i_v should
accept GetIndexedPName.
ES 3.0 fixed enums for GetIntegeri_v and GetInteger64i_v

These functions have a first parameter named "target", not "pname".
Fixed now.