IO Buffer Instantiation Override

[peteut]

What is the envisaged way to override IO buffers instantiation, like IBUFS_GTE2 for Xilinx_Family7?
For now, I reverted 3fc5f17 in my branch to allow for direct instantiation of buffers.

[whitequark]

platform.request("foo", dir="-") gives you an inout (or a p, n diffpair) that isn't connected to a buffer.

[peteut]

That perfect, thanks @whitequark.