Extend i4b to support CAPI manager based ISDN controllers (CAPI manager is
part of c4b, CAPI for BSD). This may be a preparation to add CAPI for BSD to
the source tree, in case the decision to MFC c4b itself is positive. Until
then users of c4b at least do not need to build a new kernel or base system
to compile and run c4b.
Approved by: hm (mentor)
3ce9cac735