Do not show hint to use NAT traversal if user uses private or loopback
address as a peer address.

This avoids misleading displaying in otherwise legitimate cases -
transmissions over loopback or behind NAT but just inside LAN.

Use UINT32_MAX for sizes first. This may help if WAV file is incorrectly
closed indicating that the size values aren't valid (at least FFmpeg
understands it so).

+ fixed message for overflow

This modernizes the code and makes the semantic of prototypes more clear.

Enable querying location of executable

-add function get_exec_path and C++ wrapper around it

Do not assume that initialization of null device must succeed - eg. in
some errorneous setup there may be API mismatch leading to init failed.

Was printed NULL ("(null)") because *fmt was set to NULL early.

[rtp] fix display_buf_increase_warning warning

rtp_set_recv_buf returns TRUE on success, which is #define'd to 1. Fix the logic in the check so the warning does not print erroneously.

SDL cflags define '-Dmain=SDL_main' otherwise leading to wrong main func
signature (perhaps SDL.h has some magic that corrects that but it isn't
included by our main.cpp).

FIX: SDL/SDL2 includes were missing in module CXXFLAGS, causing incompatibility on Ubuntu 20.04 with clang-10

Avoid needless seeks - data chunk must follow fmt chunk [1] thus the
file can be read without seeking (without the file size check).

[1] http://www.tactilemedia.com/info/MCI_Control_Info.html

Thread was not correctly stopped causing crashes.

Shouldn't make a difference but just to be consistent.

Similarly to WAV reader write UINT32_MAX as a placeholder if file is
longer than 4 GiB

Has data chunk size set to UINT32_MAX and size is deduced from file
length. This is consistent to what FFmpeg (MediaInfo, MPV and perhaps
others) does.

For debugging only.

GCC complains on that with -Wattributes

ANYSIZE_ARRAY is defined to 1 in Windows winnt.h

Exitting is done with ptread_cancel() since EWS' serverStop() doesn't look
to stop the thread (it supposes that close() of the socket causes
interrupting accept() of the same socket, which isn't true in U21.04
and it is a hack anyway).