Update ast spec about uint literals

compiler/vm.nim

@@ -1276,7 +1276,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
     of opcNSetIntVal:
       decodeB(rkNode)
       var dest = regs[ra].node
-      if dest.kind in {nkCharLit..nkInt64Lit} and
+      if dest.kind in {nkCharLit..nkUInt64Lit} and
          regs[rb].kind in {rkInt}:
         dest.intVal = regs[rb].intVal
       else:

doc/astspec.txt

@@ -23,7 +23,7 @@ contains:
       case kind: NimNodeKind           ## the node's kind
       of nnkNone, nnkEmpty, nnkNilLit:
         discard                        ## node contains no additional fields
-      of nnkCharLit..nnkInt64Lit:
+      of nnkCharLit..nnkUInt64Lit:
         intVal: biggestInt             ## the int literal
       of nnkFloatLit..nnkFloat64Lit:
         floatVal: biggestFloat         ## the float literal