Work on task #14780: Add debug helper asserts to ensure threading/locking requirements are met

Add LWIP_ASSERT_CORE_LOCKED() to several more places

Fix follow-up to [bug #52315] Minor typo in output of MIB compiler
LWIP_SNMP_OBJ_ID_LEN -> SNMP_MAX_OBJ_ID_LEN

Reformat SNMP code using astylerc

-Wconversion (still far from finished) and other minor compilation fixes...

SNMP: Advertise SNMPv3 support

A few more SNMPv3 cleanups

Several Win32 compile fixes in SNMP code

Add framework MIB and USM mib if SNMPv3 is enabled.

Fix bug #50427: SNMP: ifIndex should use netif_get_index()
We have netif_get_index(netif) now

Make lwIP compile with clang -Wdocumentation -> several documentation fixes

Implement consistent IPx_ADDR_ANYx macro naming between IPv4 and IPv6
- rename IP4_ADDR_ANY to IP4_ADDR_ANY4
- IP4_ADDR_ANY (= IP_ADDR_ANY) is now IPv4 any address in ip_addr_t format

minor: whitespace cleanups

Relete SNMP README and incorporate it's text in doxygen docs

Move MIB compiler to contrib, it's a better place for it

Integrate snmp_agent.txt in doxygen documentation, delete outdated file

Documentation review with Simon, minor changes

Document apps in doxygen module style, create more top-level categories to structure documentation

minor: coding style fixes

Fix alignment warnings in snmp agent - we know these structs are aligned according to requirements when they are casted because they have been instantiated as the target type (clang)

SNMP doxygen updates

minor: coding style cleanup in snmp code

snmp: don't assert-fail on zero-length OID

Fix several doxygen errors all over the code

Avoid divisions / module in SNMP code on stupid compilers

Signed-off-by: goldsimon <goldsimon@gmx.de>

SNMP: Move MIB2 interfaces subtree to separate file to get snmp_mib2.c smaller

snmp: Fix snmp_oid_to_ip for IPADDR_ANY_TYPE ips

Implement support for IP_ANY_TYPE in SNMP

Found some struct instances that can be const

Fix type on snmp_set_test_ok to be snmp_err_t

This function was returning values from snmp_err_t but wasn't
upgraded to using the typedef after commit babce70

This resulted in compilation failure on MSVC 2013

SNMP: Fix InetAddress octet string encoding (length was missing)

SNMP: SMEMCPY should only be used when size is known at compile time

SNMP: Fix shadowing warning pointed out by Erik Ekman

Fix compile of SNMP on MSVC

SNMP: Move common MIB code into snmp_core.c helper functions

Start working on udpEndpointTable

SNMP: Cleanup snmp IP helper functions, add IPv6 support

SNMP: Fix compile when IPV4 is not enabled

C-Style comments only, please

SNMP agent rewrite

- SNMPv2c support
- Greatly reduced RAM usage, no memory pools any more
- API cleanup
- MIB2 is separated from SNMP stack
- Support for multiple MIBs (snmp_set_mibs call) - e.g. for private MIB
- Improved MIB2 implementation (tcpConnTable etc.)
- Redesigned simple and generic API for MIB implementation
- Comfortable node types for scalar arrays and tables
- Counter64, bit and truthvalue datatype support
- Callbacks for SNMP writes
- Runs on two APIs: RAW and netconn
- Async API is gone - the stack now supports netconn API instead,
so blocking operations can be done in MIB calls.
SNMP runs in a worker thread when netconn API is used.
- Simplified thread sync support for MIBs - useful when MIBs
need to access variables shared with other threads without locking
(used in MIB2 to access lwIP stats from lwIP thread)

Currently in work:
- Traps rewrite
- MIB compiler