Attempt to make buttons themed

[Jonathan Wilson]

Doing a dump of the imports table from native uxtheme.dll from my XPSP2 
box, I see that it imports a function from user32.dll called 
RegisterUserApiHook which is totally undocumented (neither MSDN or google 
show up any info about what it does).
This function is only present in Windows XP (and I assume Server 2003 which 
also has uxtheme).
Based on the name, I suspect that it is a function that lets uxtheme hook 
user32 api calls (without documentation or code to that function, I cant 
really say anything more)