refactor sizealignoffset (#12077)

* small refactoring
* refactor computeObjectOffsetFoldFunction with AccumObject
* refactor packed object offstes fold function
* refactor compute union object offsets fold function
* merge normal/packed object offset fold function
* compiletime offsetof in c++ inheritance objects
* enable c++ inheritance offsetof tests
* correct alignment for big sets/enums on weird 32bit platforms
* uncomputedSize -> unknownSize
* workaround for travis
* fixes win32 alignment problems

compiler/options.nim

@@ -719,3 +719,13 @@ proc `$`*(c: IdeCmd): string =
   of ideOutline: "outline"
   of ideKnown: "known"
   of ideMsg: "msg"
+
+proc floatInt64Align*(conf: ConfigRef): int16 =
+  ## Returns either 4 or 8 depending on reasons.
+  if conf.target.targetCPU == cpuI386:
+    #on Linux/BSD i386, double are aligned to 4bytes (except with -malign-double)
+    if conf.target.targetOS != osWindows:
+      # on i386 for all known POSIX systems, 64bits ints are aligned
+      # to 4bytes (except with -malign-double)
+      return 4
+  return 8