feat(generic): Preliminary support for 64-bit floats

[scottlaird]

To use this, declare a PDO in ethercat.xml with
halType="float-double-ieee".

This is currently completely untested. It compiles. That's all I can
promise.

Issue #115

[scottlaird]

• master
  • feat(generic): Preliminary support for 64-bit floats #116 👈

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[MetalMusings]

Hi Scott, Hakan from the linuxcnc forum here. I'll add the diff against sittner's repo:
I attach the patch in a file
lcec-64bitfloatadded.patch

Basically the same as you, but I have the write of lreal when not well aligned in a record, as well. (At least that's I think what is
happening). Modeled after how it was done for float.
This has been running for days, with the right result, read and write. Not tested with lreal in a record, though.

[scottlaird]

I think I'm going to go ahead and merge this as-is, and we can revisit the float-in-record case, as well as potentially things like 53-bit-ints-in-doubles and other ways of abusing floats when someone has hardware that actually uses it. Any objection?