MFC r299162,r299163:

r299162:

Only install NIS section 8 manpages if MK_NIS != no

r299163:

Fix r299162

share/man/man8/Makefile:

• Add src.opts.mk so MK_NIS can be tested
• Fix typo in MK_NIS conditional

tools/build/mk/OptionalObsoleteFiles.inc:

• Remove WIP diff from ^/user/ngie/detangle-rc