update SDL2 to v2.30.0

add static library files for zlib

update zlib to v1.3.1

Also fixed issues with the d_netcmd.c file/folder adding logic.

Aren't used and definitely should not be in here anymore

SteelT authored 4 years ago and James R. committed 4 years ago

(cherry picked from commit 6fcc06bf72cf3b95c30f04919e807c7aaacec68d)

(cherry picked just the libcurl stuff)

Which should resolve those undefined references errors with libpng.
Rebuilt zlib just to be safe.

This reverts merge request !435

This reverts commit eda30fc9

This reverts merge request !434

This reverts merge request !433

Better than not updating it at all and having a inconsistency between versions reported from the header and internal lib version.

Also update libopenmpt

This reverts commit 603d5805.

This reverts commit 56bfdb71, reversing
changes made to c29cfbef.