Fixed crash in QMetaObject creation

Closes #6 by ensuring parameters pointers doesn't get invalidated by reallocations. The idea is to just create before hand the parameters sequences and only later reference the elements in the signal and slots structs. This makes the code safe since the sequences are immutable (and so cannot be reallocated)

src/nimqml/private/qmetaobject.nim

@@ -11,31 +11,34 @@ proc setup(superClass: QMetaObject,
            signals: seq[SignalDefinition],
            slots: seq[SlotDefinition],
            properties: seq[PropertyDefinition]): DosQMetaObject =
-  var dosParameters: seq[seq[DosParameterDefinition]] = @[]
+  var dosSignalParameters: seq[seq[DosParameterDefinition]] = @[]
   for i in 0..<signals.len:
     var parameters: seq[DosParameterDefinition] = @[]
     for p in signals[i].parameters:
       parameters.add(DosParameterDefinition(name: p.name.cstring, metaType: p.metaType.cint))
-    dosParameters.add(parameters)
+    dosSignalParameters.add(parameters)
 
   var dosSignals: seq[DosSignalDefinition] = @[]
   for i in 0..<signals.len:
-    let parametersCount = dosParameters[i].len.cint
+    let parametersCount = dosSignalParameters[i].len.cint
     let name = signals[i].name.cstring
-    let dosSignal = DosSignalDefinition(name: name, parametersCount: parametersCount, parameters: if parametersCount > 0: dosParameters[i][0].unsafeAddr else: nil)
+    let dosSignal = DosSignalDefinition(name: name, parametersCount: parametersCount, parameters: if parametersCount > 0: dosSignalParameters[i][0].unsafeAddr else: nil)
     dosSignals.add(dosSignal)
 
-  var dosSlots: seq[DosSlotDefinition] = @[]
+  var dosSlotParameters: seq[seq[DosParameterDefinition]] = @[]
   for i in 0..<slots.len:
-    let name = slots[i].name.cstring
-    let returnMetaType = slots[i].returnMetaType.cint
-    let parametersCount = slots[i].parameters.len.cint
     var parameters: seq[DosParameterDefinition] = @[]
     for p in slots[i].parameters:
       parameters.add(DosParameterDefinition(name: p.name.cstring, metaType: p.metaType.cint))
+    dosSlotParameters.add(parameters)
+
+  var dosSlots: seq[DosSlotDefinition] = @[]
+  for i in 0..<slots.len:
+    let parametersCount = dosSlotParameters[i].len.cint
+    let name = slots[i].name.cstring
+    let returnMetaType = slots[i].returnMetaType.cint
     let dosSlot = DosSlotDefinition(name: name, returnMetaType: returnMetaType,
-                                    parametersCount: parametersCount, parameters: if parameters.len > 0: parameters[0].unsafeAddr else: nil)
-    dosParameters.add(parameters)
+                                    parametersCount: parametersCount, parameters: if parametersCount > 0: dosSlotParameters[i][0].unsafeAddr else: nil)
     dosSlots.add(dosSlot)
 
   var dosProperties: seq[DosPropertyDefinition] = @[]