Get in sync with current ELF definitions. In particular this means:

Get in sync with current ELF definitions. In particular this means:
o  Remove the unused and non-standard SHT_NUM, PT_COUNT and DT_COUNT.
o  Add the STV_DEFAULT, STV_INTERNAL, STV_HIDDEN and STV_PROTECTED
   symbol visibility constants.
o  Add the ELF32_ST_VISIBILITY and ELF64_ST_VISIBILITY macros to
   get the symbol visibility from the st_other field.
o  Add the ELFOSABI_AIX, ELFOSABI_OPENVMS and ELFOSABI_NSK constants.
o  Add the ET_LOOS, ET_HIOS, ET_LOPROC and ET_HIPROC constants.
o  Further flesh out the list of machine types. Note that EM_ALPHA
   remains non-standard. The standard value for EM_ALPHA is given
   by EM_ALPHA_STD (which is a non-standard name :-)
o  Add the SHN_LOOS, SHN_HIOS and SHN_XINDEX constants.
o  Add the SHT_INIT_ARRAY, SHT_FINI_ARRAY, SHT_PREINIT_ARRAY, SHT_GROUP
   and SHT_SYMTAB_SHNDX constants.
o  Add the SHF_MERGE, SHF_STRINGS, SHF_INFO_LINK, SHF_LINK_ORDER,
   SHF_OS_NONCONFORMING, SHF_GROUP and SHF_MASKOS constants.
o  Add the PF_MASKOS and PF_MASKPROC constants.
o  Add the STB_LOOS andf STB_HIOS constants.
o  Add the STT_COMMON, STT_LOOS and STT_HIOS constants.

MFC after: 1 week