[ccan] htable license change request for Ruby

[Eric Wong]

Hello Rusty!  I am interested in using htable with mainline Ruby.
Ruby is 2-clause BSD-licensed nowadays[1].

My preliminary switch of one big st_table to htable beat out my proposed
container_of-based hash implementation (ihash) in memory usage:

    ihash:  ~100K reduction
    htable: ~150K reduction
    https://bugs.ruby-lang.org/issues/9841#change-46823

I noticed in commit d4941bf8047d16007f19a3b5b2211e1e7571f068
(htable: relicense under LGPL), there is a chance of relicensing
htable under public domain or BSD:

    So this is the simplest fix.  I might relicense under PD or BSD later,
    since the likely module should probably have an even more liberal
    license.

Therefore I kindly request the htable license be changed to a permissive
license so it may be considered for use with Ruby.

Disclaimer: I personally have a preference for copyleft, but I lack the
influence and power to change the Ruby license.  Most other Rubyists
prefer BSD/MIT-style licenses.

Anyways, thank you for htable and ccan!  I plan on switching one of my
GPL projects from gnulib hash to htable, too.

On a side note, I also started using ccan/list for Ruby:
	https://bugs.ruby-lang.org/issues/9632

[1] https://www.ruby-lang.org/en/about/license.txt