readability improvements to i386-opc.tbl

["Jan Beulich" <JBeulich at suse dot com>]

H.J.,

for a while I've been thinking about how to shrink some of the overly
long lines in that file, as that's imo severely hampering readability
(and hence maintainability). There are two pretty simple
adjustments I'd like to propose as at least a first step, but which I
wouldn't want to carry out without some prior agreement (as the
resulting patches would obviously be huge):

1) BaseIndex implies Disp{8,16,32,32S} (with a few MPX insn
exceptions, which aren't necessary as 16-bit addressing not being
legal for them is being dealt with in tc-i386.c explicitly anyway, in
md_assemble()). i386-gen could easily set those implied bits.

2) Many instructions allow no suffixes at all (in particular most of
the myriad of SIMD ones). Many other instructions allow just a
single suffix. I'd like to propose No_Suf to accompany No_*Suf
and {b,w,l,s,q,ld}Suf as the inverse of No_*Suf, to be used when
the list of permitted suffixes is shorter than the list of forbidden
ones. Again this could be dealt with in i386-gen relatively easily.

Jan