Loader: Add dynamic loader program

The dynamic loader exists as /usr/lib/Loader.so and is loaded by the
kernel when ET_DYN programs are executed.

The dynamic loader is responsible for loading the dependencies of the
main program, allocating TLS storage, preparing all loaded objects for
execution and finally jumping to the entry of the main program.

Libraries/LibELF/Image.cpp

@@ -259,6 +259,11 @@ const Image::ProgramHeader Image::program_header(unsigned index) const
     return ProgramHeader(*this, index);
 }
 
+FlatPtr Image::program_header_table_offset() const
+{
+    return header().e_phoff;
+}
+
 const Image::Relocation Image::RelocationSection::relocation(unsigned index) const
 {
     ASSERT(index < relocation_count());