Fixup the "shadow" example command to use the function that takes an execution...

Fixup the "shadow" example command to use the function that takes an execution context now that the @lldb.command decorator does the right thing for the command function that takes 5 arguments.

A few fixes:
- Check the process state to make sure it is stopped
- Grab the frame from the "exe_ctx" so this will work during breakpoint callbacks
- Print out the SBDeclaration objects of the variables that shadow each other so we can see the source locations of which variable declarations are shodowing each other.

llvm-svn: 273963