- transitioned project to CMake and deleted most of the old build system.

The EDuke32 and RedNukem frontends are working, Blood isn't yet.

Notes:

many of the CMake variables and its output still refer to zdoom. Before changing that I wanted to make sure to be able to commit something that works.
support code for Windows XP has been entirely removed. On Windows this will only target Vista and up.
the crc32.h header had to be renamed to deconflict from zlib.
several Windows API calls were changed to call the A-versions directly. Weirdly enough there were places that defined their parameters as T types but in a non-working way.
removed some remaining editor files and support for the native software rendering only Windows backend.
in a few simple cases, replaced 'char' with 'uint8_t'. The code as-is depends on chars being unsigned which is non-portable. This needs to be carefully reviewed.

source/build/include/palette.h

@@ -37,7 +37,7 @@ extern uint32_t PaletteIndexFullbrights[8];
 #define SetPaletteIndexFullbright(col) (PaletteIndexFullbrights[(col)>>5] |= (1u<<((col)&31)))
 
 typedef struct {
-    char r, g, b, f;
+    uint8_t r, g, b, f;
 } palette_t;
 typedef struct {
     uint8_t r, g, b;