x86: use %LW / %XW instead of going through vex_w_table[]

x86: use %LW / %XW instead of going through vex_w_table[]

Since we have these macros, there's no point having unnecessary table
depth.

VFPCLASSP{S,D} are now the first instance of using two %-prefixed
macros, which has pointed out a problem with the implementation. Instead
of using custom code in various case blocks, do the macro accumulation
centralized at the top of the main loop of putop(), and zap the
accumulated macros at the bottom of that loop once it has been
processed.