[merge request] Some librep patches.

[Teika Kazura <teika lavabit com>]

Hi. Please merge my librep branch.
* remove-hook-by-name didn't work, but does now.
* new function `fuction-name' returns the name of a function.
* bugfix in remove-hook; it used to emit an error if the hook
  was unbound.
* "Module limits" section in the info describes cases where mutual open
  of modules fails.

Regards,
Teika (Teika kazura)