Load file portability code for big endian.

Warning: only loads, doesn't save.
Fix for memory leak. And add forgotten break
Fix uninitialized
Prevent lock
Don't send -1 bytes. There is such check everythere. But if we add it in side funciton the logic will change
Add a check (reported by Coverity)
Portability saving fixes for big endian systems.

Saves should now be portable from big endian to little endian systems
though I need someone to actually test it to be sure I didn't mess up.
Merge branch 'big_endian_save'
Fix use-after-free of toxav's TimerHandler

If msi.c:timer_terminate_session frees "handler", then when msi.c:timer_poll's thread resumes, there WILL be a use after free of "handler", with a likely segfault.

This use after free causes a crash in qTox, see tux3/qTox#534
Merge branch 'master' of https://github.com/xor2003/toxcore

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Merge branch 'toxav-uaf' of https://github.com/tux3/toxcore

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Fixed possible threading issues.
Modify DHT.md to render correctly
Merge branch 'irdan-irdan/doc-fix'
Initial friend finding might work a bit better.
Fix typo: romdom->random
Fix DHT memory leak

Found with valgrind, in the order of magnitude of 100kB leaked
Merge branch 'master' of https://github.com/tux3/toxcore

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Update README.md
Update TODO

qTox