might dump file paths that allows the dumping of full paths or just the
basenames. Switched the stack frame dumping code to use just the basenames for
the files instead of the full path.

Modified the StackID class to no rely on needing the start PC for the current
function/symbol since we can use the SymbolContextScope to uniquely identify
that, unless there is no symbol context scope. In that case we can rely upon
the current PC value. This saves the StackID from having to calculate the 
start PC when the StackFrame::GetStackID() accessor is called.

Also improved the StackID less than operator to correctly handle inlined stack
frames in the same stack.

llvm-svn: 112867