Mention securelevel 3 as affecting ipfw and dummynet.  Generalize comment about fdisk and securelevel 2. PR:		docs/7785
Mention securelevel 3 as affecting ipfw and dummynet.  Generalize comment
about fdisk and securelevel 2.
PR:		docs/7785

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