<rdar://problem/13183720>

Provide a mechanism through which users can disable loading the Python scripts from dSYM files
This relies on a target setting: target.load-script-from-symbol-file which defaults to false ("do NOT load the script")
You need to set it to true before creating your target (or in your lldbinit file if you constantly rely on this feature) to allow the scripts to load

llvm-svn: 181709