appears to prevent a bug whereby multiple threads attempt to force one of the
promises at the same time, causing the promise to believe it is being used
recursively. All Framework tests passed (on OS X) after making this change, not
that I really expect the icons to be particularly crucial to the tests.
svn: r16820
* Another big chunk of v4-require-isms
* Allow `#lang framework/keybinding-lang' for keybinding files
* Move hierlist sources into "mrlib/hierlist", leave stub behind
svn: r10689
