This removes Makefile.depends. Instead, '.d' files are included from the 'dep'
directory. This speeds up building because dependencies for every file don't
need to be regenerated if only one changes.

As a bonus, dependencies also won't be generated if only clean type targets
are going to be run. Also added a 'distclean' target, which cleans both
objects and dependency files.

Remove Direct Draw from Makefile

See merge request STJr/SRB2!1263

Echo filenames when compiling without ECHO=1

See merge request STJr/SRB2!1260

MINGW/MINGW64 implies SDL.

Remove direct definition for D__USE_MINGW_ANSI_STDIO, as the latest standards consider this to be deprecated.

Cmake: fullscreen fix

See merge request STJr/SRB2!1226

Fix compiling using cmake if internal libs is used

See merge request STJr/SRB2!1225

Use SSE3 in 32-bit x86 binaries

See merge request STJr/SRB2!1213

All because of a typo

Add multithreading option for CMake

See merge request STJr/SRB2!1204

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

See merge request STJr/SRB2!1191

2.2.8 prep

See merge request STJr/SRB2!1170

Fix uninitialized variable issue in patches with missing grAb chunks

See merge request STJr/SRB2!1171

Prevent Canarivore gas from teleporting up walls

See merge request STJr/SRB2!1154

Fix #178

Closes #178

See merge request STJr/SRB2!1112

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

Closes #281

See merge request STJr/SRB2!1169

Fix graphics replacements not taking effect via -file

See merge request STJr/SRB2!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 STJr/SRB2!1166