MFC r233113:

MFC r233113:

 Hide kernel option ROUTETABLES evaluations in the implementation
 rather than the header file.  With this also move RT_MAXFIBS and
 RT_NUMFIBS into the implemantion to avoid further usage in other
 code. rt_numfibs is all that should be needed.

 This allows users to change the number of FIBs from 1..RT_MAXFIBS(16)
 dynamically using the tunable without the need to change the kernel
 config for the maximum anymore.  This means that the multi-FIB
 feature is now fully available with GENERIC kernels.
 The kernel option ROUTETABLES can still be used to set the default
 numbers of FIBs in absence of the tunable.

git-svn-id: svn://svn.freebsd.org/base/stable/9@235103 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f