Adds printing of the .gdb_index section header
and the -I dwarfdump option to select that section.
Got the new files added into git.
Now we access and print the gdbindex header
and the CU list.
Now gets and prints the gdbindex type unit list.
This adds implementation for the gdb_index address area.
Now we can print the gdb_index symboltable data too.
libdwarf: removed newly introduced indent errors and removed
newly introduced trailing whitespace.
dwarfdump, dwarfdump2: Fixed indentation issues
and removed trailing whitespace.
The text of a warning message from dwarfdump and dwarfdump2
was messed up. Fixed. Added a comma needed in dwarfdump.c
to avoid a coredump.
Fixes a mistake in checking a offset in dwarf_die_deliv.c
The mistake resulted in an error-return on a really really
short .debug_types section where there
was no error.

Removes unused local variables.
Switches a couple struct members (in dwarf_opaque.h) from
Dwarf_Word to Dwarf_Unsigned.
libdwarf:
dwarf_arange.c(dwarf_get_aranges_list): Remove the length variable
   as its calculated value is unused.  rename length to area_length
   for clarity.  Calculate arange_ptr_past_end early and
   correctly.  Ensure that the test for version 4 is a >=
   to reflect normal standards upgrades.
dwarf_die_deliv.c(dwarf_find_offdie_CU_Context): Add commentary
   about offsets and lengths for clarity.
   Rename fields for clarity about local vs global offset.
   Use the newly named fields for precise tests of section overflow of
   a type unit.
Other changes in libdwarf were additions and modifications of commentary.