Add better logic to turn individual shared-bindings features on and off.

[dhalbert]

Need to coordinate across main.c, Makefile, and mpconfigport.h. Could add more stuff to mpconfigboard.h and/or mpconfigboard.mk. A single change should control the feature properly everywhere.

Motivated by #333 (comment).

[sommersoft]

@deshipu brought this up in today's weekly meeting. Being on my phone and text only, I was a little late in getting some thoughts into the discussion.

I am going to need to implement a way to disable/enable the pulseio.FrequencyIn sub-module, since it leaves very little memory/flash left (or doesn't fit) on non-express SAMD boards.

My initial thought was to try and just #ifdef it in/out of shared-bindings with a #define HAS_FREQ_IN in mpconfigboard.h. I'm not even sure if that would work, or what sort of long define structure that approach would harvest. But, I think I've seen that as a non-desirable approach though a few PR reviews, anyway.

I don't necessarily want to tack this onto my pending PR, as I'm making some other changes already in samd-peripherals. Just want to be "ready" or at least discuss the direction that we want to go with this. I'm also fine with testing any suggested approaches with my use-case...

[dhalbert]

Closed in favor of #1434, which is a duplicate but written up more clearly.