* change API of apply_relocate_add() to accept ELF section name

* add ELF utility functions:
 - elf_get_symbol_shndx()
 - elf_get_common_size()
 - elf_get_common_objects()
 - elf_get_symbol_size()

* adapt module so that more complex executables may be loaded, i.e.

 - allocate "common" objects in relocatable executables
 - relocate ".data" sections
 - add elf utility fuctions

NOTE: these changes are an experimental mess at this time and must not be merged
      to master until properly tidied up