Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Always assign WARNS using ?=

- fix some nearby style bugs
- include Makefile.inc where it makes sense and reduces duplication

Approved by: ed (co-mentor)

Bump the version of all non-symbol-versioned shared libraries in
preparation for 8.0-RELEASE. Add the previous version of those
libraries to ObsoleteFiles.inc and bump __FreeBSD_Version.

Reviewed by: kib
Approved by: re (rwatson)

- Bump share library version which were missed in last bump

Reported by: jhb
Discussed with: deischen, des, doubg, harti
Approved by: re (kensmith)

Bump the shared library version number of all libraries that have not
been bumped since RELENG_5.

Reviewed by: ru
Approved by: re (not needed for commit check but in principle...)

For variables that are only checked with defined(), don't provide
any fake value.

Bump the shared library version number for the bsnmp v1.6 import
because of incompatible interface changes.

Make NULL a (void*)0 whereever possible, and fix the warnings(-Werror)
that this provokes. "Wherever possible" means "In the kernel OR NOT
C++" (implying C).

There are places where (void *) pointers are not valid, such as for
function pointers, but in the special case of (void *)0, agreement
settles on it being OK.

Most of the fixes were NULL where an integer zero was needed; many
of the fixes were NULL where ascii <nul> ('\0') was needed, and a
few were just "other".

Tested on: i386 sparc64

Clean up makefiles.

Reviewed by: harti

Add build infrastructure for libbsnmp and the modules. Add the
netgraph module for the SNMP daemon.