[GL 4.1] Vertex Attrib 64bit

http://www.opengl.org/registry/specs/ARB/vertex_attrib_64bit.txt

---

Create new enum VertexAttribDPointerType and add token

GL_DOUBLE

Old: void VertexAttribLPointer(uint index, int size, enum type, sizei stride, const void *pointer);
New: void VertexAttribLPointer(uint index, int size, VertexAttribDPointerType type, sizei stride, const void *pointer);

Old: void VertexArrayVertexAttribLOffsetEXT(uint vaobj, uint buffer, uint index, int size, enum type, sizei stride, intptr offset);
New: void VertexArrayVertexAttribLOffsetEXT(uint vaobj, uint buffer, uint index, int size, VertexAttribDPointerType type, sizei stride, intptr offset);

Old: void GetVertexAttribLdv(uint index, enum pname, double *params);
New: void GetVertexAttribLdv(uint index, VertexAttribParameter pname, double *params);

---

Maybe some Vector*d overloads? Very low priority, can be ignored for now.

void VertexAttribL1d(uint index, double x);
void VertexAttribL2d(uint index, double x, double y);
void VertexAttribL3d(uint index, double x, double y, double z);
void VertexAttribL4d(uint index, double x, double y, double z, double w);
void VertexAttribL1dv(uint index, const double *v);
void VertexAttribL2dv(uint index, const double *v);
void VertexAttribL3dv(uint index, const double *v);
void VertexAttribL4dv(uint index, const double *v);