Revert "Test / RFC: Reformat a few files using clang-format"

This reverts commit 8b4a8159a898795ef0fc9226dae1ce66531ad487.

We do not want to do this shortly before a release. Reformatting (buggy reformatting) may introduce new bugs.

Test / RFC: Reformat a few files using clang-format

Does it compile? Does it look good (enough)?

netifapi: add thread safe ARP APIs (task #14724)

This adds thread safe netifapi ARP cache APIs for add/remove

Reformat netifapi.c using astylerc

task #14314: include cleanups

Couple of more cleanups for task #14314 involving includes:
1) if.h name should match if_api.c due to LwIP convention and history.
Standard if.h include can be used with compatibility header in
posix/net/if.h
2) API header (if.h) should not be included in core code. This include
has been eliminated by moving the definition of IF_NAMESIZE to
netif.h as NETIF_NAMESIZE. This is now the canonical definition
and IF_NAMESIZE just maps to it to provide the standard type

Fix warning about shadowing a global variable "index" in netifapi.c

Minor compile fix in netifapi.c: Use LWIP_CONST_CAST to cast away constness

Task #14314: Add interface name/index APIs

This commit adds the following sets of interface name/index APIs:

Interface Identification APIs from RFC 3493:
* lwip_if_nametoindex (COMPAT macro if_nametoindex)
* lwip_if_indextoname (COMPAT macro if_indextoname)

netifapi:
* netifapi_netif_name_to_index
* netifapi_netif_index_to_name

netif:
* netif_name_to_index
* netif_index_to_name
* netif_num_to_index
* netif_index_to_num

Improve documentation: Some words about multiple execution contexts in lwIP

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

Some documentation cleanups and include more comments that have been already in code into doxygen docs

Restructure documentation. Create two top-level sections for thread-safe and callback-style APIs.

Document DHCP and AUTOIP API in doxygen module style

Document netif API in doxygen module style

Fix (correct) clang warning about increased alignment requirements in netifapi.c and pppapi.c

tcpip_priv.h: More flexible API by including return value in API_VAR_ALLOC macro

Fix shadowing warning (when compiling in C++) in TCPIP call API. Reported by Freddie Chopin.

Port netifapi to new simple tcpip API call method

netifapi: Eliminate wrapper struct netifapi_msg and rename netifapi_msg_msg to netifapi_msg

Implement generic API message handling
Add generic tcpip_send_api_msg function
Let netif API and netconn API use it
Decouple tcpip.c and tcpip_priv.h from netif API

netifapi.c: Fix compile when IPv4 is not enabled

netifapi: Do not pass NULL pointers for IP addresses to subsequent functions
Same as in my last commits - this avoids errors in lwIP code where ip addresses are dereferenced (e.g. for IP type checking) without handling thinking about NULL pointers.

started to move "private" header files containing implementation details to "lwip/priv/" include directory to seperate the API from the implementation.

minor/coding style: removed spaces before line ending (from file header)

worked on task #13480: added LWIP_IPV4 define - IPv4 can be disabled, leaving an IPv6-only stack (SNMP is still missing)

task #12722 (improve IPv4/v6 address handling): renamed ip_addr_t to ip4_addr_t, renamed ipX_addr_t to ip_addr_t and added IP version;
ip_addr_t is used for all generic IP addresses for the API, ip(4/6)_addr_t are only used internally or when initializing netifs or when calling version-related functions

patch #7885: modification of api modules to support FreeRTOS-MPU (don't pass stack-pointers to other threads) (based on patch by Artem Pisarenko)

fixed bug #35931: Name space pollution in api_msg.c and netifapi.c

Replaced struct ip_addr by typedef ip_addr_t to make changing the actual implementation behind the typedef easier.

Using typedefs for function prototypes and -pointers throughout the stack for clarity

Added netifapi_netif_set_addr()

netifapi.h, netifapi.c: add function netifapi_netif_set_default. Change the common function to reduce a little bit the footprint (for all functions using only the "netif" parameter).

netifapi.h, netifapi.c: add functions netifapi_netif_set_up, netifapi_netif_set_down, netifapi_autoip_start and netifapi_autoip_stop. Use a common function to reduce a little bit the footprint (for all functions using only the "netif" parameter).

Minor changes (but in lot of files): add #if/#endif for options where they could miss. #if LWIP_xxx if always put after #include "lwip/opt.h" (note this one indirectly include cc.h). Move others includes inside #if/#endif block.

Comments Fix for Doxygen documentation

netifapi.h, netifapi.c, tcpip.h, tcpip.c: Update code to handle the option LWIP_TCPIP_CORE_LOCKING, and do some changes to be coherent with last modifications in api_lib/api_msg (use pointers and not type with table, etc...)

Add LWIP_TCPIP_CORE_LOCKING option (0 as default value) to experiment "locking" as feature to communicate with tcpip_thread for sequential API (netconn & socket layers). Add a alternative code for lwip_sendto to how the code can be optimized with such feature....

Done some work on task #1549 (function documentation) and minor changes to meet coding standard

sockets.c, api_lib.c, api_msg.h, api_msg.c, netifapi.h, netifapi.c, tcpip.c: Include a function pointer instead of a table index in the message to reduce footprint. Disable some part of lwip_send and lwip_sendto if some options are not set (LWIP_TCP, LWIP_UDP, LWIP_RAW).

opt.h, tcpip.h, tcpip.c, netifapi.h, netifapi.c: New configuration option LWIP_NETIF_API allow to use thread-safe functions to add/remove netif in list, and to start/stop dhcp clients, using new functions from netifapi.h. Disable as default (no port change to do).