Fix for x86_op record for ocaml bindings

[ctk21]

This PR fixes a bug with the x86_op record in the ocaml bindings.

Before the change fields such as size where returned with bad values, for example:

Platform: X86 64 (Intel syntax)
0x1000	push	rbp
	Prefix:
	Opcode: 0x55
	addr_size: 8
	modrm: 0x0
	sib: 0x0
	op_count: 1
		op[0]: REG = rbp  [sz=2944]

After the change the fields are correctly returned to ocaml:

Platform: X86 64 (Intel syntax)
0x1000	push	rbp
	Prefix:
	Opcode: 0x55
	addr_size: 8
	modrm: 0x0
	sib: 0x0
	op_count: 1
		op[0]: REG = rbp  [sz=8]

[aquynh]

merged, thanks!

i also cherry-picked this for "v4" & "next" branches, please confirm they all work well.

do you mind looking at non-x86 arches? i think they need update, too.

[ctk21]

do you mind looking at non-x86 arches? i think they need update, too.

Took a look at the non-x86 arches, the code for them looked fine already!