Handling of VST "externalAttributes" when re-serializing VSTs.

[CharlesHolbrow]

When the parser encounters a VST object like the one below, it puts the externalAttributes in the FXCHAIN object, as opposed to in the VST object.

• Double check that this doesn't result in duplicated structs when parsing a VST and then re-serializing it.
• Think about what the "correct" behavior should be and implement it if needed.

<FXCHAIN
  WNDRECT 464 263 1279 576
  SHOW 0
  LASTSEL 0
  DOCKED 0
  BYPASS 0 0 0
  <VST "VST: ReaComp (Cockos)" reacomp.vst.dylib 0 "" 1919247213<5653547265636D726561636F6D700000> ""
    bWNlcu9e7f4EAAAAAQAAAAAAAAACAAAAAAAAAAQAAAAAAAAACAAAAAAAAAACAAAAAQAAAAAAAAACAAAAAAAAAFQAAAAAAAAAAAAAAA==
    776t3g3wrd6bJAA+0tNVPQAAAAB8ppE8cbkLPAAAAAAAAIA/PBIXPAAAAAAAAAAAvTeGNQAAgD8AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
    AHN0b2NrIC0gc3RlYWR5IHJvY2sga2ljawAAAAAA
  >
  PRESETNAME "stock - steady rock kick"
  FLOATPOS 0 0 0 0
  FXID {477B50A1-B9B9-BC4B-8E20-8C3E2917A24F}
  WAK 0 0
>