Log Message:
* take maintainership
* set LICENSE=ruby-license
* back to use extconf from gems.
  C ext ruby module from gems install header files into unwanted location.
  It confuse build of package using those modules.
  Moreover, gems module will not be loaded by rb_require from C module.
  It introduce unwanted behaviour to packages using directly/indirectly
  using the module.

Bump PKGREVISION.