feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

vendor/sdl-3.0.0/build-scripts/updaterev.sh

@@ -0,0 +1,49 @@
+#!/bin/sh
+#
+# Generate a header file with the current source revision
+
+outdir=`pwd`
+cd `dirname $0`
+srcdir=..
+header=$outdir/include/SDL3/SDL_revision.h
+dist=
+vendor=
+
+while [ "$#" -gt 0 ]; do
+    case "$1" in
+        (--dist)
+            dist=yes
+            shift
+            ;;
+        (--vendor)
+            vendor="$2"
+            shift 2
+            ;;
+        (*)
+            echo "$0: Unknown option: $1" >&2
+            exit 2
+            ;;
+    esac
+done
+
+rev=`sh showrev.sh 2>/dev/null`
+if [ "$rev" != "" ]; then
+    if [ -n "$dist" ]; then
+        echo "$rev" > "$outdir/VERSION.txt"
+    fi
+    echo "/* Generated by updaterev.sh, do not edit */" >"$header.new"
+    if [ -n "$vendor" ]; then
+        echo "#define SDL_VENDOR_INFO \"$vendor\"" >>"$header.new"
+    fi
+    echo "#ifdef SDL_VENDOR_INFO" >>"$header.new"
+    echo "#define SDL_REVISION \"SDL-$rev (\" SDL_VENDOR_INFO \")\"" >>"$header.new"
+    echo "#else" >>"$header.new"
+    echo "#define SDL_REVISION \"SDL-$rev\"" >>"$header.new"
+    echo "#endif" >>"$header.new"
+    echo "#define SDL_REVISION_NUMBER 0" >>"$header.new"
+    if diff $header $header.new >/dev/null 2>&1; then
+        rm "$header.new"
+    else
+        mv "$header.new" "$header"
+    fi
+fi