Add new variants of the IF_ADDR_*LOCK*() macros used for protecting interface address lists that distinguish read locks from write locks. To preserve the KPI, the previous operations are mapped to the write lock macros.  The lock is still kept as a mutex for now.
Add new variants of the IF_ADDR_*LOCK*() macros used for protecting
interface address lists that distinguish read locks from write locks.
To preserve the KPI, the previous operations are mapped to the write
lock macros.  The lock is still kept as a mutex for now.

Reviewed by:	bz
MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase