StackFrame objects now own ValueObjects for any frame variables (locals, args,

function statics, file globals and static variables) that a frame contains. 
The StackFrame objects can give out ValueObjects instances for
each variable which allows us to track when a variable changes and doesn't
depend on variable names when getting value objects.

StackFrame::GetVariableList now takes a boolean to indicate if we want to
get the frame compile unit globals and static variables.

The value objects in the stack frames can now correctly track when they have
been modified. There are a few more tweaks needed to complete this work. The
biggest issue is when stepping creates partial stacks (just frame zero usually)
and causes previous stack frames not to match up with the current stack frames
because the previous frames only has frame zero. We don't really want to 
require that all previous frames be complete since stepping often must check
stack frames to complete their jobs. I will fix this issue tomorrow.

llvm-svn: 112800