[readelf] Handle .gdb_index section version 9

[readelf] Handle .gdb_index section version 9

Add the abilitity to print a v9 .gdb_index section.

The v9 section contains an extra table, which is printed as follows:
...
Shortcut table:
Language of main: Fortran 95
Name of main: contains_keyword
...

[ For the example, I used the exec of gdb test-case
gdb.fortran/nested-funcs-2-exp when running the test-case with target board
cc-with-gdb-index. ]

Tested on x86_64-linux.

Approved-By: Nick Clifton <nickc@redhat.com>