Fixed an expression parsing issue where if you were stopped somewhere without

debug information and you evaluated an expression, a crash would occur as a
result of an unchecked pointer.

Added the ability to get the expression path for a ValueObject. For a rectangle
point child "x" the expression path would be something like: "rect.top_left.x".
This will allow GUI and command lines to get ahold of the expression path for
a value object without having to explicitly know about the hierarchy. This
means the ValueObject base class now has a "ValueObject *m_parent;" member.
All ValueObject subclasses now correctly track their lineage and are able
to provide value expression paths as well.

Added a new "--flat" option to the "frame variable" to allow for flat variable
output. An example of the current and new outputs:

(lldb) frame variable 
argc = 1
argv = 0x00007fff5fbffe80
pt = {
  x = 2
  y = 3
}
rect = {
  bottom_left = {
    x = 1
    y = 2
  }
  top_right = {
    x = 3
    y = 4
  }
}
(lldb) frame variable --flat 
argc = 1
argv = 0x00007fff5fbffe80
pt.x = 2
pt.y = 3
rect.bottom_left.x = 1
rect.bottom_left.y = 2
rect.top_right.x = 3
rect.top_right.y = 4


As you can see when there is a lot of hierarchy it can help flatten things out.
Also if you want to use a member in an expression, you can copy the text from
the "--flat" output and not have to piece it together manually. This can help
when you want to use parts of the STL in expressions:

(lldb) frame variable --flat
argc = 1
argv = 0x00007fff5fbffea8
hello_world._M_dataplus._M_p = 0x0000000000000000
(lldb) expr hello_world._M_dataplus._M_p[0] == '\0'

llvm-svn: 116532