Improving the previous checkin about target.load-script-from-symbol-file

There are two settings:
target.load-script-from-symbol-file is a boolean that says load or no load (default: false)
target.warn-on-script-from-symbol-file is also a boolean, it says whether you want to be warned when a script file is not loaded due to security (default: true)

the auto loading on change for target.load-script-from-symbol-file is preserved

llvm-svn: 182336