[PATCH] Add new script add-abilist.py

[Roland McGrath]

> Can we change the format of the abi-list file so that it is a list of
> rows, with space-separated columns
> 
>  <version> <symbol> <flags/size>
> 
> ?  Then I can write the diffing and merging logic just with sort and
> comm.  With the current format, I'd have to write another Python script
> (or learn awk).

Everyone should learn awk anyway.  But yes, I think it would be fine to
change the format to whatever is most convenient for maintenance.  The
original choices of format were somewhat motivated by keeping the files
smaller, but the scale of the file sizes in today's world makes this a
nonissue.