[gdb] Fix typos in gdb/dwarf2

[gdb] Fix typos in gdb/dwarf2

Fix the following typos:
...
gdb/dwarf2/cooked-index-shard.c:296: re-use ==> reuse
gdb/dwarf2/read-gdb-index.c:629: re-use ==> reuse
gdb/dwarf2/read.c:2399: re-using ==> reusing
gdb/dwarf2/read.c:11692: endianity ==> endianness
gdb/dwarf2/read.c:11694: endianity ==> endianness
gdb/dwarf2/read.c:11696: endianity ==> endianness
gdb/dwarf2/read.c:11709: endianity ==> endianness
...

Add aranges to the ignore list.

Also replace readin by "read_in".

Approved-By: Simon Marchi <simon.marchi@efficios.com>