Pull htab_eq_string from gcc libiberty

[Tom Tromey]

Richard> Well the obvious way around the latter issue is to get rid of the single
Richard> top-level include altogether and move the exported headers to say
Richard> libiberty/include, bfd/include opcodes/include, etc.  Then each
Richard> interface would pretty much stand on its own.

Makes sense to me.
Maybe we could name these directories after their parent directory, so
the includes would look like "libiberty/mumble.h" or "bfd/bfd.h".
Speaking hypothetically.

Submodules would also let us move other things out, like zlib and
readline.  For readline in particular this would be a big help.

Richard> Not that I'm volunteering to do this at present, just a suggestion if we
Richard> wanted to clean this up... :)

Yeah.  It's also just hard to coordinate a change like this politically,
as there are a lot of veto points in the system.

Tom