Cmake: fullscreen fix

See merge request STJr/SRB2!1226

Fix compiling using cmake if internal libs is used

See merge request !1225

Use SSE3 in 32-bit x86 binaries

See merge request !1213

All because of a typo

Add multithreading option for CMake

See merge request !1204

Fix gzip failing to compress SRB2's objdump on non-Windows.

See merge request !1191

2.2.8 prep

See merge request !1170

Fix uninitialized variable issue in patches with missing grAb chunks

See merge request !1171

Prevent Canarivore gas from teleporting up walls

See merge request !1154

Fix #178

Closes #178

See merge request !1112

Remove "The OpenGL renderer is incomplete" notice (closes #281)

Closes #281

See merge request !1169

Fix graphics replacements not taking effect via -file

See merge request !1168

This reverts commit 569453ee.

And one line from b6089ccd.

This is needed for graphics replacements to take effect.

Fix net ids broken AGAIN (closes #310)

Closes #310

See merge request !1166

This is so netvars registered by any lua scripts will load in the correct order.

Credits changes

See merge request !1161

Replaced some of the lower resolution variants with some smoother downscales. The 16x16 one is even Sonic's 1-up icon from the game!