Undocumented version constraints

Things should document Qt versions in which they were added. This information is used when making tools working with multiple Qt versions such as language bindings.

1. Added in 5.6 to QChar:
   • Script_Ahom
   • Script_AnatolianHieroglyphs
   • Script_Hatran
   • Script_Multani
   • Script_OldHungarian
   • Script_SignWriting
2. Added in 5.11 to QChar:
   • Script_Adlam
   • Script_Bhaiksuki
   • Script_Marchen
   • Script_Newa
   • Script_Osage
   • Script_Tangut
   • Script_MasaramGondi
   • Script_Nushu
   • Script_Soyombo
   • Script_ZanabazarSquare

• # Added in 5.11 to QIODevice:
  • NewOnly
  • ExistingOnly
• # Added in 5.12 to Qt namespace:
  • WA_StyleSheetTarget
• # Added in 5.12 to QGradient:
  • ObjectMode-