LLDB: API for iPermission of object file's sections

    
 Summary:
 - Added an API to public interface that provides permissions (RWX) of
   individual sections of an object file
   
 - Earlier, there was no way to find out this information through SB
   APIs
    
 - A possible use case of this API is:
   when a user wants to know the sections that have executable machine
   instructions and want to write a tool on top of LLDB based on this
   information

 - Differential Revision: https://reviews.llvm.org/D24251

llvm-svn: 280924