Somwhere in Micropython there's a `<io.TextIOWrapper 0>` from
vfs_posix_file that's getting garbage collected and which in turn
triggers the object's __del__ which then in turn attempt to close FD 0.

Let's not allow that to happen by adding some ugly hardcoded deny list
for FD 0,1,2 in the close function.

Ideally, we would figure out why that object exists, why it gets garbage
collect and what really should happen here. But this is good enough.

Slight adjustment of gradient stops to distribute primary colors better
on characters of flow3r. Use single precision constants rather than
double precision constants for coordinates.

This reverts commit ed827e7b.

Pushed by accident.

1. We weren't setting bProtocol to IAD (technically required for CDC-ACM
   devices which have IAD)
2. We weren't counting the IAD pseudo-interface as one of the two
   interfaces in the configuration.

How did that get here.

This reverts commit 4f0a4b80b4137e1a192111fd330eb819d45c8764.

This is a first-pass implementation of an SD card driver, implementing
both low-level block-based access and mounting to VFS.

Not sure I like this, but let's test it out.