[gdb/contrib] Add spellcheck.sh

I came across a table containing common misspellings [1], and wrote a script to
detect and correct these misspellings.

The table also contains entries that have alternatives, like this:
...
addres->address, adders
...
and for those the script prints a TODO instead.

The script downloads the webpage containing the table, extracts the table and
caches it in .git/wikipedia-common-misspellings.txt to prevent downloading it
over and over again.

Example usage:
...
$ gdb/contrib/spellcheck.sh gdb*
...

ChangeLog files are silently skipped.

Checked with shellcheck.

Tested on x86_64-linux, by running it on the gdb* dirs on doing a build and
test run.

The results of running it are in the two following patches.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>

[1] https://en.wikipedia.org/wiki/Wikipedia:Lists_of_common_misspellings/For_machines
1 file changed