Full big num implementation with preferred serialization and 65-bit negs (#219)

Encoding and decoding of negative big numbers now takes into account the offset of 1 for all CBOR negative numbers. Also, big numbers are encoded with preferred serialization -- when they can be encoded with type 0 and type 1 integers, they are. Encoding and decoding big numbers is no longer a pass through for tagging a binary string.

This is an incompatible change with QCBOR 1.x. A mode configuration call is added to return to the 1.x behavior if desired.

This is because of the realization in work on 65-bit negative numbers that big numbers need preferred serialization.

This affects big floats and decimal fractions when the mantissa is a big number.

New methods to encode big numbers with non-preferred serialization are added.

A new method is added to process a raw big number for the offset of one for negatives. This is outside of spiffy decode. It does a little big number arithmetic.

dCBOR numeric reduction now includes 65-bit integers both for number encoding and decoding.



* Checkpoint work on 65-bit negs

* check point ... mostly working

* Checkpoint work on preferred bignums

* Tests passing...

* bignum encode improved to near completion

* Fix #ifdef fan out and error condition bug

* Code tidiness

* debugging unreplicatable CI failure

* v1 compat mode; EAM encode test fan out starting

* debugging ci...

* hacking ci failures

* CI failure hacking

* CI hacking

* Clean up some left over junk

* more leftover junk

* Clean up test leftovers

* Fixes for #ifdef fan out

* Fix conversion of uint to zero, even though it's never used

* REmove more junk

---------

Co-authored-by: Laurence Lundblade <lgl@securitytheory.com>
diff --git a/src/ieee754.h b/src/ieee754.h
index c82b9b4..fed28f1 100644
--- a/src/ieee754.h
+++ b/src/ieee754.h
@@ -97,6 +97,7 @@
 struct IEEE754_ToInt {
    enum {IEEE754_ToInt_IS_INT,
          IEEE754_ToInt_IS_UINT,
+         IEEE754_ToInt_IS_65BIT_NEG,
          IEEE754_ToInt_NO_CONVERSION,
          IEEE754_ToInt_NaN
    } type;