[Lazarus] Change descendance of TPage from TCustomControl to TScrollBox

[Felipe Ferreira da Silva]

I think that the change of the descendance of TPage from TCustomControl 
to TScrollBox would make more sense, since the component TNotebook is 
used more for configuration windows. Sometimes, you need to add a lot of 
controls inside the TPage, but there is no space, then you have to add a 
TScrollBox for each TPage. It increases the size of the program and cost 
memory space.

I just tried here, change "TPage = class(TCustomControl)" to "TPage = 
class(TScrollBox)" has no collateral effect.

- Felipe Ferreira