Add a temporary hack to change the various non-build related special
targets like 'cscope' and 'glimpse' to not depend on src.opts.mk or
bsd.*.mk.

Reviewed by:	imp
- Shrink the list of excluded modules to what actually still doesn't build
  as of r266799.
- Some style cleanups.

MFC after:	1 week
- Actually, modules are built correctly when compiled along the kernel as
  they then pick up an opt_global.h from KERNBUILDDIR having PAE defined.
  Thus, build all modules by default except those which still really are
  defective as of r266799.
- Minor style cleanup.

MFC after:	1 week