Document x87 instruction provenance about x86reference HOT 2 OPEN

I think it should be noted that most if not all FP instructions are missing the proc attribute for when the instruction was first introduced.
It's also worth noting that with 80387 processor instruction, a new proc value should be added and not rely on the value 03: 80386 because according to Wikipedia:

Released in 1987, a full two years after the 386 chip

Unlike other FP instructions that were introduced with FPU that were released together with their counter-part like the 80287.

from x86reference.

The missing proc attribute is because most of the FP instructions were introduced with 8087.

The 03 means 80387 in this case, the docs are not correct.

from x86reference.