Support unsigned 64-bit integers for sequence numbers

[JohnGreenan]

Per https://www.fixtrading.org/groups/continuousmkts/
Sequence number resets are a bore.

The implementation proposed is to use an unsigned 64 bit integer for a sequence number.

Using 1 billion sequence numbers per second, that will last for 584 years until they run out.

So we can leave the problem to our great, great, great (more) grandchildren to solve!

Would be good to include a set of test cases so that testing w
Continuous Markets WG- 24x7 FIX Best Practise Working Draft_v0.015.docx
ith a counterpart engine that maybe uses an int32 or uint32 can be picked up quickly. And cover all the other values that use the seqnum "datatype"

See attached "[Continuous Markets WG- 24x7 FIX Best Practise Working Draft_v0.015.docx]

[JohnGreenan]

See also
da4089/simplefix#50
quickfix-j/quickfixj#621
#419
ferrumfix/ferrumfix#108
connamara/quickfixn#760
paritytrading/philadelphia#365
jcass77/WTFIX#8
real-logic/artio#480

[JohnGreenan]

Now adopted https://www.fixtrading.org/packages/fix-recommended-practices-24x7-sessions/