This allows MC to match data32 ... as one instruction instead of two (data32 without insn + insn).
The compatibility with GNU as improves: data32 ljmp will be matched as ljmpl.
data32 lgdt 4(%eax) will be matched as lgdtl (prefixes: 0x67 0x66, instead
of 0x66 0x67).
GNU as supports many other data32 *w as *l. We currently just hard code
data32 callw and data32 ljmpw. Generalizing the suffix replacement is
tricky and requires a think about the "bwlq" appending suffix rules in MatchAndEmitATTInstruction.